Fwd: Question about kernel interfaces

Fwd: Question about kernel interfaces

[Siddhartha De]

I have already asked this question on the kernelnewbies IRC but I
wanted a bit of feedback from the Linux gurus ...


Is sysfs 'supposed' to be a read only where various kernel parameters
are exposed to be read ? Or are they 'supposed' to be writable too ?

Are all drivers in future required to expose interfaces in sysfs ?

If the answer to the above is true , then would we be really requiring
IOCTL calls at all anymore ... because all that we would need to do to
make a driver do something is to change values in some of the files in
sysfs ... for eg to call a ioctl called DO_SOMETHING on driver D1 we
would be doing :

echo 1> /sysfs/D1/IOCTLS/DO_SOMETHING  ( or something like that ... :) )

Are there any plans of exposing the kernel api ( that is syscalls and
libc ) as sysfs files ... for eg

echo 1> /sysfs/libc/get_system_time
cat /sysfs/libc/results/system_time

Would it be a good idea to do this ?

How about exposing core system calls , libc and any new libraries over
http/over the network  ? This would make calling ioctls and really low
level stuff from high level languages like Java a trivial process .
For eg right now if I wanted to call some function say foo () in
library my_library.so in Java I would have to take the JNI/JNA route
... doable but not exactly 'easy' ( same for other high level
languages ) ... whereas in the new way all I would have to do is send
a request to say :-
  http://localhost:7000/my_library/foo?arg1=something,arg2=something
( Just wanted a frank discussion on this idea .... )



Thanking you in anticipation ,

 Yours sincerely ,

  Kernel newbie

Re: Question about kernel interfaces

[One Thousand Gnomes]

> Is sysfs 'supposed' to be a read only where various kernel parameters
> are exposed to be read ? Or are they 'supposed' to be writable too ?

You can create either

> Are all drivers in future required to expose interfaces in sysfs ?

Only if they need one (some will appear automatically as you enable power
management and the like).
 
> If the answer to the above is true , then would we be really requiring
> IOCTL calls at all anymore ... because all that we would need to do to
> make a driver do something is to change values in some of the files in
> sysfs ... for eg to call a ioctl called DO_SOMETHING on driver D1 we
> would be doing :
> 
> echo 1> /sysfs/D1/IOCTLS/DO_SOMETHING  ( or something like that ... :) )

Try implementing a few this way and you'll discover you can't. ioctls
happen on file handles which are tied to instances of an object not to
the driver. ioctl also allows read/write pairs so can be serializing and
sequenced in a way sysfs can't.

> Are there any plans of exposing the kernel api ( that is syscalls and
> libc ) as sysfs files ... for eg
> 
> echo 1> /sysfs/libc/get_system_time
> cat /sysfs/libc/results/system_time

Time is an example where you could implement it via sysfs. It's an
unusual case in that its global and stateless.

> Would it be a good idea to do this ?

No, probably not.
 
> How about exposing core system calls , libc and any new libraries over
> http/over the network  ? This would make calling ioctls and really low
> level stuff from high level languages like Java a trivial process .
> For eg right now if I wanted to call some function say foo () in
> library my_library.so in Java I would have to take the JNI/JNA route
> ... doable but not exactly 'easy' ( same for other high level
> languages ) ... whereas in the new way all I would have to do is send
> a request to say :-
>   http://localhost:7000/my_library/foo?arg1=something,arg2=something
> ( Just wanted a frank discussion on this idea .... )

Except that you've also got to transfer the data and the authentication
back and forth. You need much more than sysfs for this, you need some way
to pass messages securely, and to do work on a remote node on your
behalf. You need some way to locate a resource.

It's not entirely impossible to make syscalls remotable. It's been done to
some extent at least two ways. Read up on plan 9 (which did try and take
Unix much more networked and within the classic tradition of Unix as a
small clean OS), and perhaps also on MOSIX, which took a very different
approach to running on a cluster of boxes as one instance. Another odd
example to look at is Minix. Minix treats all syscalls internally as
messages between user processes and services like the file system. Minix
never really made use of it, but it does mean its much easier to do
remote syscall models in Minix than Linux. (in part I suspect this comes
from Tanenbaum's Amoeba and similar work).

I'm not sure I'd pick Java for this either - Java is very weak in this
area as it tends to expose notions of locality and what is and isn't
remote when doing method invocations. Languages like smalltalk on the
other hand got this right many years before.

Alan
 

Re: Question about kernel interfaces

[Siddhartha De]

Hi  ,

Thanks for your reply . Really appreciate your taking time out to
answer this ...

1>
> Are all drivers in future required to expose interfaces in sysfs ?

> Only if they need one (some will appear automatically as you enable power
management and the like).

Just wanted to point out something  :-

Quoting from makelinux website :-
http://www.makelinux.net/books/lkd2/ch17lev1sec8

"The sysfs filesystem is currently the place for implementing
functionality previously reserved for ioctl() calls on device nodes or
the procfs filesystem. These days, the chic thing to do is implement
such functionality as sysfs attributes in the appropriate directory.
For example, instead of a new ioctl() on a device node, add a sysfs
attribute in the driver's sysfs directory. Such an approach avoids the
type-unsafe use of obscure ioctl() arguments and the haphazard mess of
/proc. "


Quoting from the busybox mailing list archives :-

Hi vda, all,

ISTR that sysfs was the long-term plan of the kernel folks and that they
mean to completely(?) drop ioctl support.

In what timeframe should we migrate to "pure" sysfs and drop using
any ioctls (if a sysfs interface exists)?


cheers,
Bernhard

Quote from livejournal

http://zaitcev.livejournal.com/84788.html


sysfs is the new ioctl



With all these spread all over the net , any newbie like myself is
bound to get confused ... add to that I just saw some old mails from
Linus where he blasts the ioctl way of doing things (
http://yarchive.net/comp/linux/ioctl.html )  :)


2> It's not entirely impossible to make syscalls remotable. It's been done to
some extent at least two ways. Read up on plan 9 (which did try and take
Unix much more networked and within the classic tradition of Unix as a
small clean OS),

Thanks for the advice , I did read up a bit on Plan 9 , but from what
I understood it was trying to abstract the network
to the user ... a bit different from what my confusion is .... but a
great resource nevertheless

3>


>I'm not sure I'd pick Java for this either - Java is very weak in this
area as it tends to expose notions of locality and what is and isn't
remote when doing method invocations. Languages like smalltalk on the
other hand got this right many years before.


Yeah ... the reason I mentioned Java is because it represents a
typical high level language commonly used by today's programmers ...
the problem with all these languages is that while they do a fine job
when writing web based applications they really make it difficult to
access low level system calls ( for eg talking to the driver and stuff
) . Moreover when a library is written for say Linux or Windows the
library becomes tied to that particular language ( the one it is
written in ) ... for eg let us say we write a new library in C for
playing mp3 's in Linux ... if we are to write a user space program
and want to access the library 's functionality we have to write the
userspace program in C ... if we write it in any other language ( say
Java ) we have to use other methods like Java Native Interface ( JNI
... or more recently JNA ) to access this ... not  a good way .

          What I am saying is let us expose the library over http/any
other network protocol ... if any other language needs to access the
library's functionality it simply makes a request like :-

 http://localhost:7000/libmp3/foo?arg1=something&arg2=something

This way we avoid a lot of rework since once a library is written it's
functionality is exposed to all languages ( Java / PHP / Python )  .

Taking this idea further , could we also expose driver IOCTL's over
the network ?

For eg to open the cd rom drive we would be calling the following url :-

(assuming device is /dev/cdrom )


http://localhost:7000/IOCTL/IOCTL_EJECT?device=/dev/cdrom

The listener program ( our interpreter listening on port 7000 ) would
be taking this url call and doing the actual IOCTL call

file_handle= open ( /dev/cdrom )
call_IOCTL ( file_handle,IOCTL_EJECT, &some_structure )

The idea of exposing all these interfaces as url's is not to make them
accessible over the network ( although this could be a possibility
...)  but simply to make them accessible from any user space program
in a language neutral way ...


Thanks

Kernel Newbie    :)





On Thu, Jan 8, 2015 at 7:18 PM, One Thousand Gnomes
<gnomes@lxorguk.ukuu.org.uk> wrote:
>> Is sysfs 'supposed' to be a read only where various kernel parameters
>> are exposed to be read ? Or are they 'supposed' to be writable too ?
>
> You can create either
>
>> Are all drivers in future required to expose interfaces in sysfs ?
>
> Only if they need one (some will appear automatically as you enable power
> management and the like).
>
>> If the answer to the above is true , then would we be really requiring
>> IOCTL calls at all anymore ... because all that we would need to do to
>> make a driver do something is to change values in some of the files in
>> sysfs ... for eg to call a ioctl called DO_SOMETHING on driver D1 we
>> would be doing :
>>
>> echo 1> /sysfs/D1/IOCTLS/DO_SOMETHING  ( or something like that ... :) )
>
> Try implementing a few this way and you'll discover you can't. ioctls
> happen on file handles which are tied to instances of an object not to
> the driver. ioctl also allows read/write pairs so can be serializing and
> sequenced in a way sysfs can't.
>
>> Are there any plans of exposing the kernel api ( that is syscalls and
>> libc ) as sysfs files ... for eg
>>
>> echo 1> /sysfs/libc/get_system_time
>> cat /sysfs/libc/results/system_time
>
> Time is an example where you could implement it via sysfs. It's an
> unusual case in that its global and stateless.
>
>> Would it be a good idea to do this ?
>
> No, probably not.
>
>> How about exposing core system calls , libc and any new libraries over
>> http/over the network  ? This would make calling ioctls and really low
>> level stuff from high level languages like Java a trivial process .
>> For eg right now if I wanted to call some function say foo () in
>> library my_library.so in Java I would have to take the JNI/JNA route
>> ... doable but not exactly 'easy' ( same for other high level
>> languages ) ... whereas in the new way all I would have to do is send
>> a request to say :-
>>   http://localhost:7000/my_library/foo?arg1=something,arg2=something
>> ( Just wanted a frank discussion on this idea .... )
>
> Except that you've also got to transfer the data and the authentication
> back and forth. You need much more than sysfs for this, you need some way
> to pass messages securely, and to do work on a remote node on your
> behalf. You need some way to locate a resource.
>
> It's not entirely impossible to make syscalls remotable. It's been done to
> some extent at least two ways. Read up on plan 9 (which did try and take
> Unix much more networked and within the classic tradition of Unix as a
> small clean OS), and perhaps also on MOSIX, which took a very different
> approach to running on a cluster of boxes as one instance. Another odd
> example to look at is Minix. Minix treats all syscalls internally as
> messages between user processes and services like the file system. Minix
> never really made use of it, but it does mean its much easier to do
> remote syscall models in Minix than Linux. (in part I suspect this comes
> from Tanenbaum's Amoeba and similar work).
>
> I'm not sure I'd pick Java for this either - Java is very weak in this
> area as it tends to expose notions of locality and what is and isn't
> remote when doing method invocations. Languages like smalltalk on the
> other hand got this right many years before.
>
> Alan
>

Fwd: Question about kernel interfaces

[Siddhartha De]

Hi ,

Dear Kernel Newbies ,

I have had some discussions regarding this on the IRC but I thought it
would be a better idea to post it to the mailing list as well ....
just in case someone came up with any ideas/comments/suggestions later
....


PS :- I am marking a copy to the main linux-kernel list so that any
discussions automatically gets forwarded there ...

Thanks ,

Kernel Newbie :)


---------- Forwarded message ----------
From: Siddhartha De <siddhartha.de87@gmail.com>
Date: Fri, Jan 9, 2015 at 5:18 PM
Subject: Re: Question about kernel interfaces
To: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>
Cc: linux-kernel <linux-kernel@vger.kernel.org>


Hi  ,

Thanks for your reply . Really appreciate your taking time out to
answer this ...

1>
> Are all drivers in future required to expose interfaces in sysfs ?

> Only if they need one (some will appear automatically as you enable power
management and the like).

Just wanted to point out something  :-

Quoting from makelinux website :-
http://www.makelinux.net/books/lkd2/ch17lev1sec8

"The sysfs filesystem is currently the place for implementing
functionality previously reserved for ioctl() calls on device nodes or
the procfs filesystem. These days, the chic thing to do is implement
such functionality as sysfs attributes in the appropriate directory.
For example, instead of a new ioctl() on a device node, add a sysfs
attribute in the driver's sysfs directory. Such an approach avoids the
type-unsafe use of obscure ioctl() arguments and the haphazard mess of
/proc. "


Quoting from the busybox mailing list archives :-

Hi vda, all,

ISTR that sysfs was the long-term plan of the kernel folks and that they
mean to completely(?) drop ioctl support.

In what timeframe should we migrate to "pure" sysfs and drop using
any ioctls (if a sysfs interface exists)?


cheers,
Bernhard

Quote from livejournal

http://zaitcev.livejournal.com/84788.html


sysfs is the new ioctl



With all these spread all over the net , any newbie like myself is
bound to get confused ... add to that I just saw some old mails from
Linus where he blasts the ioctl way of doing things (
http://yarchive.net/comp/linux/ioctl.html )  :)


2> It's not entirely impossible to make syscalls remotable. It's been done to
some extent at least two ways. Read up on plan 9 (which did try and take
Unix much more networked and within the classic tradition of Unix as a
small clean OS),

Thanks for the advice , I did read up a bit on Plan 9 , but from what
I understood it was trying to abstract the network
to the user ... a bit different from what my confusion is .... but a
great resource nevertheless

3>


>I'm not sure I'd pick Java for this either - Java is very weak in this
area as it tends to expose notions of locality and what is and isn't
remote when doing method invocations. Languages like smalltalk on the
other hand got this right many years before.


Yeah ... the reason I mentioned Java is because it represents a
typical high level language commonly used by today's programmers ...
the problem with all these languages is that while they do a fine job
when writing web based applications they really make it difficult to
access low level system calls ( for eg talking to the driver and stuff
) . Moreover when a library is written for say Linux or Windows the
library becomes tied to that particular language ( the one it is
written in ) ... for eg let us say we write a new library in C for
playing mp3 's in Linux ... if we are to write a user space program
and want to access the library 's functionality we have to write the
userspace program in C ... if we write it in any other language ( say
Java ) we have to use other methods like Java Native Interface ( JNI
... or more recently JNA ) to access this ... not  a good way .

          What I am saying is let us expose the library over http/any
other network protocol ... if any other language needs to access the
library's functionality it simply makes a request like :-

 http://localhost:7000/libmp3/foo?arg1=something&arg2=something

This way we avoid a lot of rework since once a library is written it's
functionality is exposed to all languages ( Java / PHP / Python )  .

Taking this idea further , could we also expose driver IOCTL's over
the network ?

For eg to open the cd rom drive we would be calling the following url :-

(assuming device is /dev/cdrom )


http://localhost:7000/IOCTL/IOCTL_EJECT?device=/dev/cdrom

The listener program ( our interpreter listening on port 7000 ) would
be taking this url call and doing the actual IOCTL call

file_handle= open ( /dev/cdrom )
call_IOCTL ( file_handle,IOCTL_EJECT, &some_structure )

The idea of exposing all these interfaces as url's is not to make them
accessible over the network ( although this could be a possibility
...)  but simply to make them accessible from any user space program
in a language neutral way ...


Thanks

Kernel Newbie    :)





On Thu, Jan 8, 2015 at 7:18 PM, One Thousand Gnomes
<gnomes@lxorguk.ukuu.org.uk> wrote:
>> Is sysfs 'supposed' to be a read only where various kernel parameters
>> are exposed to be read ? Or are they 'supposed' to be writable too ?
>
> You can create either
>
>> Are all drivers in future required to expose interfaces in sysfs ?
>
> Only if they need one (some will appear automatically as you enable power
> management and the like).
>
>> If the answer to the above is true , then would we be really requiring
>> IOCTL calls at all anymore ... because all that we would need to do to
>> make a driver do something is to change values in some of the files in
>> sysfs ... for eg to call a ioctl called DO_SOMETHING on driver D1 we
>> would be doing :
>>
>> echo 1> /sysfs/D1/IOCTLS/DO_SOMETHING  ( or something like that ... :) )
>
> Try implementing a few this way and you'll discover you can't. ioctls
> happen on file handles which are tied to instances of an object not to
> the driver. ioctl also allows read/write pairs so can be serializing and
> sequenced in a way sysfs can't.
>
>> Are there any plans of exposing the kernel api ( that is syscalls and
>> libc ) as sysfs files ... for eg
>>
>> echo 1> /sysfs/libc/get_system_time
>> cat /sysfs/libc/results/system_time
>
> Time is an example where you could implement it via sysfs. It's an
> unusual case in that its global and stateless.
>
>> Would it be a good idea to do this ?
>
> No, probably not.
>
>> How about exposing core system calls , libc and any new libraries over
>> http/over the network  ? This would make calling ioctls and really low
>> level stuff from high level languages like Java a trivial process .
>> For eg right now if I wanted to call some function say foo () in
>> library my_library.so in Java I would have to take the JNI/JNA route
>> ... doable but not exactly 'easy' ( same for other high level
>> languages ) ... whereas in the new way all I would have to do is send
>> a request to say :-
>>   http://localhost:7000/my_library/foo?arg1=something,arg2=something
>> ( Just wanted a frank discussion on this idea .... )
>
> Except that you've also got to transfer the data and the authentication
> back and forth. You need much more than sysfs for this, you need some way
> to pass messages securely, and to do work on a remote node on your
> behalf. You need some way to locate a resource.
>
> It's not entirely impossible to make syscalls remotable. It's been done to
> some extent at least two ways. Read up on plan 9 (which did try and take
> Unix much more networked and within the classic tradition of Unix as a
> small clean OS), and perhaps also on MOSIX, which took a very different
> approach to running on a cluster of boxes as one instance. Another odd
> example to look at is Minix. Minix treats all syscalls internally as
> messages between user processes and services like the file system. Minix
> never really made use of it, but it does mean its much easier to do
> remote syscall models in Minix than Linux. (in part I suspect this comes
> from Tanenbaum's Amoeba and similar work).
>
> I'm not sure I'd pick Java for this either - Java is very weak in this
> area as it tends to expose notions of locality and what is and isn't
> remote when doing method invocations. Languages like smalltalk on the
> other hand got this right many years before.
>
> Alan
>


On Wednesday Jan 7th Siddhartha De (siddhartha.de87@gmail.com ) wrote :-


I have already asked this question on the kernelnewbies IRC but I
wanted a bit of feedback from the Linux gurus ...


Is sysfs 'supposed' to be a read only where various kernel parameters
are exposed to be read ? Or are they 'supposed' to be writable too ?

Are all drivers in future required to expose interfaces in sysfs ?

If the answer to the above is true , then would we be really requiring
IOCTL calls at all anymore ... because all that we would need to do to
make a driver do something is to change values in some of the files in
sysfs ... for eg to call a ioctl called DO_SOMETHING on driver D1 we
would be doing :

echo 1> /sysfs/D1/IOCTLS/DO_SOMETHING  ( or something like that ... :) )

Are there any plans of exposing the kernel api ( that is syscalls and
libc ) as sysfs files ... for eg

echo 1> /sysfs/libc/get_system_time
cat /sysfs/libc/results/system_time

Would it be a good idea to do this ?

How about exposing core system calls , libc and any new libraries over
http/over the network  ? This would make calling ioctls and really low
level stuff from high level languages like Java a trivial process .
For eg right now if I wanted to call some function say foo () in
library my_library.so in Java I would have to take the JNI/JNA route
... doable but not exactly 'easy' ( same for other high level
languages ) ... whereas in the new way all I would have to do is send
a request to say :-


http://localhost:7000/my_library/foo?arg1=something,arg2=something  (
Just wanted a frank discussion on this idea .... )



Thanking you in anticipation ,

 Yours sincerely ,

  Kernel newbie

Fwd: Question about kernel interfaces

[Siddhartha De]

Hi ,

Dear Kernel Newbies ,

I have had some discussions regarding this on the IRC but I thought it
would be a better idea to post it to the mailing list as well ....
just in case someone came up with any ideas/comments/suggestions later
....


PS :- I am marking a copy to the main linux-kernel list so that any
discussions automatically gets forwarded there ...

Thanks ,

Kernel Newbie :)


---------- Forwarded message ----------
From: Siddhartha De <siddhartha.de87@gmail.com>
Date: Fri, Jan 9, 2015 at 5:18 PM
Subject: Re: Question about kernel interfaces
To: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>
Cc: linux-kernel <linux-kernel@vger.kernel.org>


Hi  ,

Thanks for your reply . Really appreciate your taking time out to
answer this ...

1>
> Are all drivers in future required to expose interfaces in sysfs ?

> Only if they need one (some will appear automatically as you enable power
management and the like).

Just wanted to point out something  :-

Quoting from makelinux website :-
http://www.makelinux.net/books/lkd2/ch17lev1sec8

"The sysfs filesystem is currently the place for implementing
functionality previously reserved for ioctl() calls on device nodes or
the procfs filesystem. These days, the chic thing to do is implement
such functionality as sysfs attributes in the appropriate directory.
For example, instead of a new ioctl() on a device node, add a sysfs
attribute in the driver's sysfs directory. Such an approach avoids the
type-unsafe use of obscure ioctl() arguments and the haphazard mess of
/proc. "


Quoting from the busybox mailing list archives :-

Hi vda, all,

ISTR that sysfs was the long-term plan of the kernel folks and that they
mean to completely(?) drop ioctl support.

In what timeframe should we migrate to "pure" sysfs and drop using
any ioctls (if a sysfs interface exists)?


cheers,
Bernhard

Quote from livejournal

http://zaitcev.livejournal.com/84788.html


sysfs is the new ioctl



With all these spread all over the net , any newbie like myself is
bound to get confused ... add to that I just saw some old mails from
Linus where he blasts the ioctl way of doing things (
http://yarchive.net/comp/linux/ioctl.html )  :)


2> It's not entirely impossible to make syscalls remotable. It's been done to
some extent at least two ways. Read up on plan 9 (which did try and take
Unix much more networked and within the classic tradition of Unix as a
small clean OS),

Thanks for the advice , I did read up a bit on Plan 9 , but from what
I understood it was trying to abstract the network
to the user ... a bit different from what my confusion is .... but a
great resource nevertheless

3>


>I'm not sure I'd pick Java for this either - Java is very weak in this
area as it tends to expose notions of locality and what is and isn't
remote when doing method invocations. Languages like smalltalk on the
other hand got this right many years before.


Yeah ... the reason I mentioned Java is because it represents a
typical high level language commonly used by today's programmers ...
the problem with all these languages is that while they do a fine job
when writing web based applications they really make it difficult to
access low level system calls ( for eg talking to the driver and stuff
) . Moreover when a library is written for say Linux or Windows the
library becomes tied to that particular language ( the one it is
written in ) ... for eg let us say we write a new library in C for
playing mp3 's in Linux ... if we are to write a user space program
and want to access the library 's functionality we have to write the
userspace program in C ... if we write it in any other language ( say
Java ) we have to use other methods like Java Native Interface ( JNI
... or more recently JNA ) to access this ... not  a good way .

          What I am saying is let us expose the library over http/any
other network protocol ... if any other language needs to access the
library's functionality it simply makes a request like :-

 http://localhost:7000/libmp3/foo?arg1=something&arg2=something

This way we avoid a lot of rework since once a library is written it's
functionality is exposed to all languages ( Java / PHP / Python )  .

Taking this idea further , could we also expose driver IOCTL's over
the network ?

For eg to open the cd rom drive we would be calling the following url :-

(assuming device is /dev/cdrom )


http://localhost:7000/IOCTL/IOCTL_EJECT?device=/dev/cdrom

The listener program ( our interpreter listening on port 7000 ) would
be taking this url call and doing the actual IOCTL call

file_handle= open ( /dev/cdrom )
call_IOCTL ( file_handle,IOCTL_EJECT, &some_structure )

The idea of exposing all these interfaces as url's is not to make them
accessible over the network ( although this could be a possibility
...)  but simply to make them accessible from any user space program
in a language neutral way ...


Thanks

Kernel Newbie    :)





On Thu, Jan 8, 2015 at 7:18 PM, One Thousand Gnomes
<gnomes@lxorguk.ukuu.org.uk> wrote:
>> Is sysfs 'supposed' to be a read only where various kernel parameters
>> are exposed to be read ? Or are they 'supposed' to be writable too ?
>
> You can create either
>
>> Are all drivers in future required to expose interfaces in sysfs ?
>
> Only if they need one (some will appear automatically as you enable power
> management and the like).
>
>> If the answer to the above is true , then would we be really requiring
>> IOCTL calls at all anymore ... because all that we would need to do to
>> make a driver do something is to change values in some of the files in
>> sysfs ... for eg to call a ioctl called DO_SOMETHING on driver D1 we
>> would be doing :
>>
>> echo 1> /sysfs/D1/IOCTLS/DO_SOMETHING  ( or something like that ... :) )
>
> Try implementing a few this way and you'll discover you can't. ioctls
> happen on file handles which are tied to instances of an object not to
> the driver. ioctl also allows read/write pairs so can be serializing and
> sequenced in a way sysfs can't.
>
>> Are there any plans of exposing the kernel api ( that is syscalls and
>> libc ) as sysfs files ... for eg
>>
>> echo 1> /sysfs/libc/get_system_time
>> cat /sysfs/libc/results/system_time
>
> Time is an example where you could implement it via sysfs. It's an
> unusual case in that its global and stateless.
>
>> Would it be a good idea to do this ?
>
> No, probably not.
>
>> How about exposing core system calls , libc and any new libraries over
>> http/over the network  ? This would make calling ioctls and really low
>> level stuff from high level languages like Java a trivial process .
>> For eg right now if I wanted to call some function say foo () in
>> library my_library.so in Java I would have to take the JNI/JNA route
>> ... doable but not exactly 'easy' ( same for other high level
>> languages ) ... whereas in the new way all I would have to do is send
>> a request to say :-
>>   http://localhost:7000/my_library/foo?arg1=something,arg2=something
>> ( Just wanted a frank discussion on this idea .... )
>
> Except that you've also got to transfer the data and the authentication
> back and forth. You need much more than sysfs for this, you need some way
> to pass messages securely, and to do work on a remote node on your
> behalf. You need some way to locate a resource.
>
> It's not entirely impossible to make syscalls remotable. It's been done to
> some extent at least two ways. Read up on plan 9 (which did try and take
> Unix much more networked and within the classic tradition of Unix as a
> small clean OS), and perhaps also on MOSIX, which took a very different
> approach to running on a cluster of boxes as one instance. Another odd
> example to look at is Minix. Minix treats all syscalls internally as
> messages between user processes and services like the file system. Minix
> never really made use of it, but it does mean its much easier to do
> remote syscall models in Minix than Linux. (in part I suspect this comes
> from Tanenbaum's Amoeba and similar work).
>
> I'm not sure I'd pick Java for this either - Java is very weak in this
> area as it tends to expose notions of locality and what is and isn't
> remote when doing method invocations. Languages like smalltalk on the
> other hand got this right many years before.
>
> Alan
>


On Wednesday Jan 7th Siddhartha De (siddhartha.de87 at gmail.com ) wrote :-


I have already asked this question on the kernelnewbies IRC but I
wanted a bit of feedback from the Linux gurus ...


Is sysfs 'supposed' to be a read only where various kernel parameters
are exposed to be read ? Or are they 'supposed' to be writable too ?

Are all drivers in future required to expose interfaces in sysfs ?

If the answer to the above is true , then would we be really requiring
IOCTL calls at all anymore ... because all that we would need to do to
make a driver do something is to change values in some of the files in
sysfs ... for eg to call a ioctl called DO_SOMETHING on driver D1 we
would be doing :

echo 1> /sysfs/D1/IOCTLS/DO_SOMETHING  ( or something like that ... :) )

Are there any plans of exposing the kernel api ( that is syscalls and
libc ) as sysfs files ... for eg

echo 1> /sysfs/libc/get_system_time
cat /sysfs/libc/results/system_time

Would it be a good idea to do this ?

How about exposing core system calls , libc and any new libraries over
http/over the network  ? This would make calling ioctls and really low
level stuff from high level languages like Java a trivial process .
For eg right now if I wanted to call some function say foo () in
library my_library.so in Java I would have to take the JNI/JNA route
... doable but not exactly 'easy' ( same for other high level
languages ) ... whereas in the new way all I would have to do is send
a request to say :-


http://localhost:7000/my_library/foo?arg1=something,arg2=something  (
Just wanted a frank discussion on this idea .... )



Thanking you in anticipation ,

 Yours sincerely ,

  Kernel newbie

Fwd: Question about kernel interfaces

[Siddhartha De]

Looks like the last message bounced ...


Thanks ,

Kernel Newbie :)




---------- Forwarded message ----------
From: Siddhartha De <siddhartha.de87@gmail.com>
Date: Fri, Jan 9, 2015 at 5:50 PM
Subject: Fwd: Question about kernel interfaces
To: linux-kernel <linux-kernel@vger.kernel.org>, Siddhartha De
<siddhartha.de87@gmail.com>, kernelnewbies@kernelnewbies.org


Hi ,

Dear Kernel Newbies ,

I have had some discussions regarding this on the IRC but I thought it
would be a better idea to post it to the mailing list as well ....
just in case someone came up with any ideas/comments/suggestions later
....


PS :- I am marking a copy to the main linux-kernel list so that any
discussions automatically gets forwarded there ...

Thanks ,

Kernel Newbie :)


---------- Forwarded message ----------
From: Siddhartha De <siddhartha.de87@gmail.com>
Date: Fri, Jan 9, 2015 at 5:18 PM
Subject: Re: Question about kernel interfaces
To: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>
Cc: linux-kernel <linux-kernel@vger.kernel.org>


Hi  ,

Thanks for your reply . Really appreciate your taking time out to
answer this ...

1>
> Are all drivers in future required to expose interfaces in sysfs ?

> Only if they need one (some will appear automatically as you enable power
management and the like).

Just wanted to point out something  :-

Quoting from makelinux website :-
http://www.makelinux.net/books/lkd2/ch17lev1sec8

"The sysfs filesystem is currently the place for implementing
functionality previously reserved for ioctl() calls on device nodes or
the procfs filesystem. These days, the chic thing to do is implement
such functionality as sysfs attributes in the appropriate directory.
For example, instead of a new ioctl() on a device node, add a sysfs
attribute in the driver's sysfs directory. Such an approach avoids the
type-unsafe use of obscure ioctl() arguments and the haphazard mess of
/proc. "


Quoting from the busybox mailing list archives :-

Hi vda, all,

ISTR that sysfs was the long-term plan of the kernel folks and that they
mean to completely(?) drop ioctl support.

In what timeframe should we migrate to "pure" sysfs and drop using
any ioctls (if a sysfs interface exists)?


cheers,
Bernhard

Quote from livejournal

http://zaitcev.livejournal.com/84788.html


sysfs is the new ioctl



With all these spread all over the net , any newbie like myself is
bound to get confused ... add to that I just saw some old mails from
Linus where he blasts the ioctl way of doing things (
http://yarchive.net/comp/linux/ioctl.html )  :)


2> It's not entirely impossible to make syscalls remotable. It's been done to
some extent at least two ways. Read up on plan 9 (which did try and take
Unix much more networked and within the classic tradition of Unix as a
small clean OS),

Thanks for the advice , I did read up a bit on Plan 9 , but from what
I understood it was trying to abstract the network
to the user ... a bit different from what my confusion is .... but a
great resource nevertheless

3>


>I'm not sure I'd pick Java for this either - Java is very weak in this
area as it tends to expose notions of locality and what is and isn't
remote when doing method invocations. Languages like smalltalk on the
other hand got this right many years before.


Yeah ... the reason I mentioned Java is because it represents a
typical high level language commonly used by today's programmers ...
the problem with all these languages is that while they do a fine job
when writing web based applications they really make it difficult to
access low level system calls ( for eg talking to the driver and stuff
) . Moreover when a library is written for say Linux or Windows the
library becomes tied to that particular language ( the one it is
written in ) ... for eg let us say we write a new library in C for
playing mp3 's in Linux ... if we are to write a user space program
and want to access the library 's functionality we have to write the
userspace program in C ... if we write it in any other language ( say
Java ) we have to use other methods like Java Native Interface ( JNI
... or more recently JNA ) to access this ... not  a good way .

          What I am saying is let us expose the library over http/any
other network protocol ... if any other language needs to access the
library's functionality it simply makes a request like :-

 http://localhost:7000/libmp3/foo?arg1=something&arg2=something

This way we avoid a lot of rework since once a library is written it's
functionality is exposed to all languages ( Java / PHP / Python )  .

Taking this idea further , could we also expose driver IOCTL's over
the network ?

For eg to open the cd rom drive we would be calling the following url :-

(assuming device is /dev/cdrom )


http://localhost:7000/IOCTL/IOCTL_EJECT?device=/dev/cdrom

The listener program ( our interpreter listening on port 7000 ) would
be taking this url call and doing the actual IOCTL call

file_handle= open ( /dev/cdrom )
call_IOCTL ( file_handle,IOCTL_EJECT, &some_structure )

The idea of exposing all these interfaces as url's is not to make them
accessible over the network ( although this could be a possibility
...)  but simply to make them accessible from any user space program
in a language neutral way ...


Thanks

Kernel Newbie    :)





On Thu, Jan 8, 2015 at 7:18 PM, One Thousand Gnomes
<gnomes@lxorguk.ukuu.org.uk> wrote:
>> Is sysfs 'supposed' to be a read only where various kernel parameters
>> are exposed to be read ? Or are they 'supposed' to be writable too ?
>
> You can create either
>
>> Are all drivers in future required to expose interfaces in sysfs ?
>
> Only if they need one (some will appear automatically as you enable power
> management and the like).
>
>> If the answer to the above is true , then would we be really requiring
>> IOCTL calls at all anymore ... because all that we would need to do to
>> make a driver do something is to change values in some of the files in
>> sysfs ... for eg to call a ioctl called DO_SOMETHING on driver D1 we
>> would be doing :
>>
>> echo 1> /sysfs/D1/IOCTLS/DO_SOMETHING  ( or something like that ... :) )
>
> Try implementing a few this way and you'll discover you can't. ioctls
> happen on file handles which are tied to instances of an object not to
> the driver. ioctl also allows read/write pairs so can be serializing and
> sequenced in a way sysfs can't.
>
>> Are there any plans of exposing the kernel api ( that is syscalls and
>> libc ) as sysfs files ... for eg
>>
>> echo 1> /sysfs/libc/get_system_time
>> cat /sysfs/libc/results/system_time
>
> Time is an example where you could implement it via sysfs. It's an
> unusual case in that its global and stateless.
>
>> Would it be a good idea to do this ?
>
> No, probably not.
>
>> How about exposing core system calls , libc and any new libraries over
>> http/over the network  ? This would make calling ioctls and really low
>> level stuff from high level languages like Java a trivial process .
>> For eg right now if I wanted to call some function say foo () in
>> library my_library.so in Java I would have to take the JNI/JNA route
>> ... doable but not exactly 'easy' ( same for other high level
>> languages ) ... whereas in the new way all I would have to do is send
>> a request to say :-
>>   http://localhost:7000/my_library/foo?arg1=something,arg2=something
>> ( Just wanted a frank discussion on this idea .... )
>
> Except that you've also got to transfer the data and the authentication
> back and forth. You need much more than sysfs for this, you need some way
> to pass messages securely, and to do work on a remote node on your
> behalf. You need some way to locate a resource.
>
> It's not entirely impossible to make syscalls remotable. It's been done to
> some extent at least two ways. Read up on plan 9 (which did try and take
> Unix much more networked and within the classic tradition of Unix as a
> small clean OS), and perhaps also on MOSIX, which took a very different
> approach to running on a cluster of boxes as one instance. Another odd
> example to look at is Minix. Minix treats all syscalls internally as
> messages between user processes and services like the file system. Minix
> never really made use of it, but it does mean its much easier to do
> remote syscall models in Minix than Linux. (in part I suspect this comes
> from Tanenbaum's Amoeba and similar work).
>
> I'm not sure I'd pick Java for this either - Java is very weak in this
> area as it tends to expose notions of locality and what is and isn't
> remote when doing method invocations. Languages like smalltalk on the
> other hand got this right many years before.
>
> Alan
>


On Wednesday Jan 7th Siddhartha De (siddhartha.de87@gmail.com ) wrote :-


I have already asked this question on the kernelnewbies IRC but I
wanted a bit of feedback from the Linux gurus ...


Is sysfs 'supposed' to be a read only where various kernel parameters
are exposed to be read ? Or are they 'supposed' to be writable too ?

Are all drivers in future required to expose interfaces in sysfs ?

If the answer to the above is true , then would we be really requiring
IOCTL calls at all anymore ... because all that we would need to do to
make a driver do something is to change values in some of the files in
sysfs ... for eg to call a ioctl called DO_SOMETHING on driver D1 we
would be doing :

echo 1> /sysfs/D1/IOCTLS/DO_SOMETHING  ( or something like that ... :) )

Are there any plans of exposing the kernel api ( that is syscalls and
libc ) as sysfs files ... for eg

echo 1> /sysfs/libc/get_system_time
cat /sysfs/libc/results/system_time

Would it be a good idea to do this ?

How about exposing core system calls , libc and any new libraries over
http/over the network  ? This would make calling ioctls and really low
level stuff from high level languages like Java a trivial process .
For eg right now if I wanted to call some function say foo () in
library my_library.so in Java I would have to take the JNI/JNA route
... doable but not exactly 'easy' ( same for other high level
languages ) ... whereas in the new way all I would have to do is send
a request to say :-


http://localhost:7000/my_library/foo?arg1=something,arg2=something  (
Just wanted a frank discussion on this idea .... )



Thanking you in anticipation ,

 Yours sincerely ,

  Kernel newbie

Fwd: Question about kernel interfaces

[Siddhartha De]

Looks like the last message bounced ...


Thanks ,

Kernel Newbie :)




---------- Forwarded message ----------
From: Siddhartha De <siddhartha.de87@gmail.com>
Date: Fri, Jan 9, 2015 at 5:50 PM
Subject: Fwd: Question about kernel interfaces
To: linux-kernel <linux-kernel@vger.kernel.org>, Siddhartha De
<siddhartha.de87@gmail.com>, kernelnewbies at kernelnewbies.org


Hi ,

Dear Kernel Newbies ,

I have had some discussions regarding this on the IRC but I thought it
would be a better idea to post it to the mailing list as well ....
just in case someone came up with any ideas/comments/suggestions later
....


PS :- I am marking a copy to the main linux-kernel list so that any
discussions automatically gets forwarded there ...

Thanks ,

Kernel Newbie :)


---------- Forwarded message ----------
From: Siddhartha De <siddhartha.de87@gmail.com>
Date: Fri, Jan 9, 2015 at 5:18 PM
Subject: Re: Question about kernel interfaces
To: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>
Cc: linux-kernel <linux-kernel@vger.kernel.org>


Hi  ,

Thanks for your reply . Really appreciate your taking time out to
answer this ...

1>
> Are all drivers in future required to expose interfaces in sysfs ?

> Only if they need one (some will appear automatically as you enable power
management and the like).

Just wanted to point out something  :-

Quoting from makelinux website :-
http://www.makelinux.net/books/lkd2/ch17lev1sec8

"The sysfs filesystem is currently the place for implementing
functionality previously reserved for ioctl() calls on device nodes or
the procfs filesystem. These days, the chic thing to do is implement
such functionality as sysfs attributes in the appropriate directory.
For example, instead of a new ioctl() on a device node, add a sysfs
attribute in the driver's sysfs directory. Such an approach avoids the
type-unsafe use of obscure ioctl() arguments and the haphazard mess of
/proc. "


Quoting from the busybox mailing list archives :-

Hi vda, all,

ISTR that sysfs was the long-term plan of the kernel folks and that they
mean to completely(?) drop ioctl support.

In what timeframe should we migrate to "pure" sysfs and drop using
any ioctls (if a sysfs interface exists)?


cheers,
Bernhard

Quote from livejournal

http://zaitcev.livejournal.com/84788.html


sysfs is the new ioctl



With all these spread all over the net , any newbie like myself is
bound to get confused ... add to that I just saw some old mails from
Linus where he blasts the ioctl way of doing things (
http://yarchive.net/comp/linux/ioctl.html )  :)


2> It's not entirely impossible to make syscalls remotable. It's been done to
some extent at least two ways. Read up on plan 9 (which did try and take
Unix much more networked and within the classic tradition of Unix as a
small clean OS),

Thanks for the advice , I did read up a bit on Plan 9 , but from what
I understood it was trying to abstract the network
to the user ... a bit different from what my confusion is .... but a
great resource nevertheless

3>


>I'm not sure I'd pick Java for this either - Java is very weak in this
area as it tends to expose notions of locality and what is and isn't
remote when doing method invocations. Languages like smalltalk on the
other hand got this right many years before.


Yeah ... the reason I mentioned Java is because it represents a
typical high level language commonly used by today's programmers ...
the problem with all these languages is that while they do a fine job
when writing web based applications they really make it difficult to
access low level system calls ( for eg talking to the driver and stuff
) . Moreover when a library is written for say Linux or Windows the
library becomes tied to that particular language ( the one it is
written in ) ... for eg let us say we write a new library in C for
playing mp3 's in Linux ... if we are to write a user space program
and want to access the library 's functionality we have to write the
userspace program in C ... if we write it in any other language ( say
Java ) we have to use other methods like Java Native Interface ( JNI
... or more recently JNA ) to access this ... not  a good way .

          What I am saying is let us expose the library over http/any
other network protocol ... if any other language needs to access the
library's functionality it simply makes a request like :-

 http://localhost:7000/libmp3/foo?arg1=something&arg2=something

This way we avoid a lot of rework since once a library is written it's
functionality is exposed to all languages ( Java / PHP / Python )  .

Taking this idea further , could we also expose driver IOCTL's over
the network ?

For eg to open the cd rom drive we would be calling the following url :-

(assuming device is /dev/cdrom )


http://localhost:7000/IOCTL/IOCTL_EJECT?device=/dev/cdrom

The listener program ( our interpreter listening on port 7000 ) would
be taking this url call and doing the actual IOCTL call

file_handle= open ( /dev/cdrom )
call_IOCTL ( file_handle,IOCTL_EJECT, &some_structure )

The idea of exposing all these interfaces as url's is not to make them
accessible over the network ( although this could be a possibility
...)  but simply to make them accessible from any user space program
in a language neutral way ...


Thanks

Kernel Newbie    :)





On Thu, Jan 8, 2015 at 7:18 PM, One Thousand Gnomes
<gnomes@lxorguk.ukuu.org.uk> wrote:
>> Is sysfs 'supposed' to be a read only where various kernel parameters
>> are exposed to be read ? Or are they 'supposed' to be writable too ?
>
> You can create either
>
>> Are all drivers in future required to expose interfaces in sysfs ?
>
> Only if they need one (some will appear automatically as you enable power
> management and the like).
>
>> If the answer to the above is true , then would we be really requiring
>> IOCTL calls at all anymore ... because all that we would need to do to
>> make a driver do something is to change values in some of the files in
>> sysfs ... for eg to call a ioctl called DO_SOMETHING on driver D1 we
>> would be doing :
>>
>> echo 1> /sysfs/D1/IOCTLS/DO_SOMETHING  ( or something like that ... :) )
>
> Try implementing a few this way and you'll discover you can't. ioctls
> happen on file handles which are tied to instances of an object not to
> the driver. ioctl also allows read/write pairs so can be serializing and
> sequenced in a way sysfs can't.
>
>> Are there any plans of exposing the kernel api ( that is syscalls and
>> libc ) as sysfs files ... for eg
>>
>> echo 1> /sysfs/libc/get_system_time
>> cat /sysfs/libc/results/system_time
>
> Time is an example where you could implement it via sysfs. It's an
> unusual case in that its global and stateless.
>
>> Would it be a good idea to do this ?
>
> No, probably not.
>
>> How about exposing core system calls , libc and any new libraries over
>> http/over the network  ? This would make calling ioctls and really low
>> level stuff from high level languages like Java a trivial process .
>> For eg right now if I wanted to call some function say foo () in
>> library my_library.so in Java I would have to take the JNI/JNA route
>> ... doable but not exactly 'easy' ( same for other high level
>> languages ) ... whereas in the new way all I would have to do is send
>> a request to say :-
>>   http://localhost:7000/my_library/foo?arg1=something,arg2=something
>> ( Just wanted a frank discussion on this idea .... )
>
> Except that you've also got to transfer the data and the authentication
> back and forth. You need much more than sysfs for this, you need some way
> to pass messages securely, and to do work on a remote node on your
> behalf. You need some way to locate a resource.
>
> It's not entirely impossible to make syscalls remotable. It's been done to
> some extent at least two ways. Read up on plan 9 (which did try and take
> Unix much more networked and within the classic tradition of Unix as a
> small clean OS), and perhaps also on MOSIX, which took a very different
> approach to running on a cluster of boxes as one instance. Another odd
> example to look at is Minix. Minix treats all syscalls internally as
> messages between user processes and services like the file system. Minix
> never really made use of it, but it does mean its much easier to do
> remote syscall models in Minix than Linux. (in part I suspect this comes
> from Tanenbaum's Amoeba and similar work).
>
> I'm not sure I'd pick Java for this either - Java is very weak in this
> area as it tends to expose notions of locality and what is and isn't
> remote when doing method invocations. Languages like smalltalk on the
> other hand got this right many years before.
>
> Alan
>


On Wednesday Jan 7th Siddhartha De (siddhartha.de87 at gmail.com ) wrote :-


I have already asked this question on the kernelnewbies IRC but I
wanted a bit of feedback from the Linux gurus ...


Is sysfs 'supposed' to be a read only where various kernel parameters
are exposed to be read ? Or are they 'supposed' to be writable too ?

Are all drivers in future required to expose interfaces in sysfs ?

If the answer to the above is true , then would we be really requiring
IOCTL calls at all anymore ... because all that we would need to do to
make a driver do something is to change values in some of the files in
sysfs ... for eg to call a ioctl called DO_SOMETHING on driver D1 we
would be doing :

echo 1> /sysfs/D1/IOCTLS/DO_SOMETHING  ( or something like that ... :) )

Are there any plans of exposing the kernel api ( that is syscalls and
libc ) as sysfs files ... for eg

echo 1> /sysfs/libc/get_system_time
cat /sysfs/libc/results/system_time

Would it be a good idea to do this ?

How about exposing core system calls , libc and any new libraries over
http/over the network  ? This would make calling ioctls and really low
level stuff from high level languages like Java a trivial process .
For eg right now if I wanted to call some function say foo () in
library my_library.so in Java I would have to take the JNI/JNA route
... doable but not exactly 'easy' ( same for other high level
languages ) ... whereas in the new way all I would have to do is send
a request to say :-


http://localhost:7000/my_library/foo?arg1=something,arg2=something  (
Just wanted a frank discussion on this idea .... )



Thanking you in anticipation ,

 Yours sincerely ,

  Kernel newbie

Re: Fwd: Question about kernel interfaces

[Valdis.Kletnieks]

[-- Attachment #1: Type: text/plain, Size: 751 bytes --]

On Fri, 09 Jan 2015 18:00:07 +0530, Siddhartha De said:

> In what timeframe should we migrate to "pure" sysfs and drop using
> any ioctls (if a sysfs interface exists)?

Pretty much the answer is "you don't", for the wsame reason that there's still
a lot of non-process stuff in /proc - there's no good way to clean up /pron up /
 proc or get rid of ioctl()'s without breaking userspace.

And some ioctl's you can't get rid of because they're part of official
standards (for instance, all to TIO_FOO stuff for controlling a terminal are
part of POSIX - removing them would break code that used to be portable...

Or to put it differently - ioctl() virst appeared in Unix Version 7 in 1979.
>From that, calculate how long it will take to get rid of.


[-- Attachment #2: Type: application/pgp-signature, Size: 848 bytes --]

Fwd: Question about kernel interfaces

[Valdis.Kletnieks at vt.edu]

On Fri, 09 Jan 2015 18:00:07 +0530, Siddhartha De said:

> In what timeframe should we migrate to "pure" sysfs and drop using
> any ioctls (if a sysfs interface exists)?

Pretty much the answer is "you don't", for the wsame reason that there's still
a lot of non-process stuff in /proc - there's no good way to clean up /pron up /
 proc or get rid of ioctl()'s without breaking userspace.

And some ioctl's you can't get rid of because they're part of official
standards (for instance, all to TIO_FOO stuff for controlling a terminal are
part of POSIX - removing them would break code that used to be portable...

Or to put it differently - ioctl() virst appeared in Unix Version 7 in 1979.
>From that, calculate how long it will take to get rid of.

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Re: Question about kernel interfaces

[One Thousand Gnomes]

> Just wanted to point out something  :-
> 
> Quoting from makelinux website :-
> http://www.makelinux.net/books/lkd2/ch17lev1sec8
> 
> "The sysfs filesystem is currently the place for implementing
> functionality previously reserved for ioctl() calls on device nodes or
> the procfs filesystem. These days, the chic thing to do is implement
> such functionality as sysfs attributes in the appropriate directory.
> For example, instead of a new ioctl() on a device node, add a sysfs
> attribute in the driver's sysfs directory. Such an approach avoids the
> type-unsafe use of obscure ioctl() arguments and the haphazard mess of
> /proc. "

And is wrong. Certainly rather clueless people had the idea they could
make ioctl go away using sysfs, and then everyone wrote about it. Anyone
who actually thought about the problem realised immediately they are not
semantically equivalent.

> sysfs is the new ioctl

And as was pointed out even then they are not semantically equivalent so
everyone who was talking about "sysfs being the new ioctl" was basically
talking out the wrong end.

What was done was to stop filling drivers with ioctls for pieces of
general information which didn't have a context attached to it or
sequence. Things like power state, what type it is, what bus it is on
etc. That avoided having zillions of ioctls but at the cost of memory.

> Taking this idea further , could we also expose driver IOCTL's over
> the network ?
> 
> For eg to open the cd rom drive we would be calling the following url :-

You could but why would you make the network visible. If you look at real
clustered systems they all hide the network. You don't care where it is,
often you don't even care where the drive is.

eject /dev/cdrom

on such a system lets the kernel figure out who to ask to eject it.

The job of an OS is to abstract details like that. In a clustered OS I
want to be able to type

	mount mydisk

and I don't care who, where or how it gets mounted so long as it appears.

Alan

Fwd: Question about kernel interfaces

[Siddhartha De]

FYI ...


---------- Forwarded message ----------
From: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>
Date: Wed, Jan 14, 2015 at 10:03 PM
Subject: Re: Question about kernel interfaces
To: Siddhartha De <siddhartha.de87@gmail.com>
Cc: linux-kernel <linux-kernel@vger.kernel.org>


> Just wanted to point out something  :-
>
> Quoting from makelinux website :-
> http://www.makelinux.net/books/lkd2/ch17lev1sec8
>
> "The sysfs filesystem is currently the place for implementing
> functionality previously reserved for ioctl() calls on device nodes or
> the procfs filesystem. These days, the chic thing to do is implement
> such functionality as sysfs attributes in the appropriate directory.
> For example, instead of a new ioctl() on a device node, add a sysfs
> attribute in the driver's sysfs directory. Such an approach avoids the
> type-unsafe use of obscure ioctl() arguments and the haphazard mess of
> /proc. "

And is wrong. Certainly rather clueless people had the idea they could
make ioctl go away using sysfs, and then everyone wrote about it. Anyone
who actually thought about the problem realised immediately they are not
semantically equivalent.

> sysfs is the new ioctl

And as was pointed out even then they are not semantically equivalent so
everyone who was talking about "sysfs being the new ioctl" was basically
talking out the wrong end.

What was done was to stop filling drivers with ioctls for pieces of
general information which didn't have a context attached to it or
sequence. Things like power state, what type it is, what bus it is on
etc. That avoided having zillions of ioctls but at the cost of memory.

> Taking this idea further , could we also expose driver IOCTL's over
> the network ?
>
> For eg to open the cd rom drive we would be calling the following url :-

You could but why would you make the network visible. If you look at real
clustered systems they all hide the network. You don't care where it is,
often you don't even care where the drive is.

eject /dev/cdrom

on such a system lets the kernel figure out who to ask to eject it.

The job of an OS is to abstract details like that. In a clustered OS I
want to be able to type

        mount mydisk

and I don't care who, where or how it gets mounted so long as it appears.

Alan

Re: Question about kernel interfaces

[Siddhartha De]

Hi Alan Thanks for your reply ... really helped a lot

>> Taking this idea further , could we also expose driver IOCTL's over
>> the network ?
>>
>> For eg to open the cd rom drive we would be calling the following url :-
>
> You could but why would you make the network visible. If you look at real
> clustered systems they all hide the network. You don't care where it is,
> often you don't even care where the drive is.
>
> eject /dev/cdrom
>
> on such a system lets the kernel figure out who to ask to eject it.
>
> The job of an OS is to abstract details like that. In a clustered OS I
> want to be able to type
>
>         mount mydisk
>
> and I don't care who, where or how it gets mounted so long as it appears.
>
> Alan

OK ... the idea of exposing driver ioctl 's or low level system calls
or library calls over the network isn't for use in clustered systems (
although it certainly could be used  there ) ... the reason I want to
expose all these systems is to provide an universal interface that any
programming language can request services from .

To bring home the point to the Linux folks let's talk about a
particular example ....

Let's say you need to call an ioctl from a shell script ( I know its a
very rare use case but please bear with me ... :) )

So the current way of doing it is probably to write a C program which
actually calls the ioctl and then call the C program from the shell
script ...

However if we exposed the IOCTL as a web url we could easily call its
services by using a simple utility like curl . So in our shell script
we would probably write :-

curl http://localhost:7000/IOCTL/IOCTL_EJECT?device=/dev/cdrom

and the IOCTL_EJECT ioctl would get called on /dev/cdrom
that is ioctl ( &handle_to_/dev/cdrom , IOCTL_EJECT , &some_buffer )
would get called ( by our translator running as a separate program or
as a service daemon )

Taking this concept further all libraries could expose their functions
via such an interface .

And the benefits would go far beyond just shell scripts . Once the
interface has been exposed any high level language can use the
functionality provided by drivers , libraries to their full extent .

If we want to expose the full power of drivers and other libraries to
the entire gamut of programmers regardless of whatever language they
are coding in , this could be a good way of doing it  :)

Thanking you ,
Yours sincerely ,
Kernel Newbie


On Sat, Jan 17, 2015 at 1:07 AM, Siddhartha De
<siddhartha.de87@gmail.com> wrote:
> FYI ...
>
>
> ---------- Forwarded message ----------
> From: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>
> Date: Wed, Jan 14, 2015 at 10:03 PM
> Subject: Re: Question about kernel interfaces
> To: Siddhartha De <siddhartha.de87@gmail.com>
> Cc: linux-kernel <linux-kernel@vger.kernel.org>
>
>
>> Just wanted to point out something  :-
>>
>> Quoting from makelinux website :-
>> http://www.makelinux.net/books/lkd2/ch17lev1sec8
>>
>> "The sysfs filesystem is currently the place for implementing
>> functionality previously reserved for ioctl() calls on device nodes or
>> the procfs filesystem. These days, the chic thing to do is implement
>> such functionality as sysfs attributes in the appropriate directory.
>> For example, instead of a new ioctl() on a device node, add a sysfs
>> attribute in the driver's sysfs directory. Such an approach avoids the
>> type-unsafe use of obscure ioctl() arguments and the haphazard mess of
>> /proc. "
>
> And is wrong. Certainly rather clueless people had the idea they could
> make ioctl go away using sysfs, and then everyone wrote about it. Anyone
> who actually thought about the problem realised immediately they are not
> semantically equivalent.
>
>> sysfs is the new ioctl
>
> And as was pointed out even then they are not semantically equivalent so
> everyone who was talking about "sysfs being the new ioctl" was basically
> talking out the wrong end.
>
> What was done was to stop filling drivers with ioctls for pieces of
> general information which didn't have a context attached to it or
> sequence. Things like power state, what type it is, what bus it is on
> etc. That avoided having zillions of ioctls but at the cost of memory.
>
>> Taking this idea further , could we also expose driver IOCTL's over
>> the network ?
>>
>> For eg to open the cd rom drive we would be calling the following url :-
>
> You could but why would you make the network visible. If you look at real
> clustered systems they all hide the network. You don't care where it is,
> often you don't even care where the drive is.
>
> eject /dev/cdrom
>
> on such a system lets the kernel figure out who to ask to eject it.
>
> The job of an OS is to abstract details like that. In a clustered OS I
> want to be able to type
>
>         mount mydisk
>
> and I don't care who, where or how it gets mounted so long as it appears.
>
> Alan

Question about kernel interfaces

[Siddhartha De]

Hi Alan Thanks for your reply ... really helped a lot

>> Taking this idea further , could we also expose driver IOCTL's over
>> the network ?
>>
>> For eg to open the cd rom drive we would be calling the following url :-
>
> You could but why would you make the network visible. If you look at real
> clustered systems they all hide the network. You don't care where it is,
> often you don't even care where the drive is.
>
> eject /dev/cdrom
>
> on such a system lets the kernel figure out who to ask to eject it.
>
> The job of an OS is to abstract details like that. In a clustered OS I
> want to be able to type
>
>         mount mydisk
>
> and I don't care who, where or how it gets mounted so long as it appears.
>
> Alan

OK ... the idea of exposing driver ioctl 's or low level system calls
or library calls over the network isn't for use in clustered systems (
although it certainly could be used  there ) ... the reason I want to
expose all these systems is to provide an universal interface that any
programming language can request services from .

To bring home the point to the Linux folks let's talk about a
particular example ....

Let's say you need to call an ioctl from a shell script ( I know its a
very rare use case but please bear with me ... :) )

So the current way of doing it is probably to write a C program which
actually calls the ioctl and then call the C program from the shell
script ...

However if we exposed the IOCTL as a web url we could easily call its
services by using a simple utility like curl . So in our shell script
we would probably write :-

curl http://localhost:7000/IOCTL/IOCTL_EJECT?device=/dev/cdrom

and the IOCTL_EJECT ioctl would get called on /dev/cdrom
that is ioctl ( &handle_to_/dev/cdrom , IOCTL_EJECT , &some_buffer )
would get called ( by our translator running as a separate program or
as a service daemon )

Taking this concept further all libraries could expose their functions
via such an interface .

And the benefits would go far beyond just shell scripts . Once the
interface has been exposed any high level language can use the
functionality provided by drivers , libraries to their full extent .

If we want to expose the full power of drivers and other libraries to
the entire gamut of programmers regardless of whatever language they
are coding in , this could be a good way of doing it  :)

Thanking you ,
Yours sincerely ,
Kernel Newbie


On Sat, Jan 17, 2015 at 1:07 AM, Siddhartha De
<siddhartha.de87@gmail.com> wrote:
> FYI ...
>
>
> ---------- Forwarded message ----------
> From: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>
> Date: Wed, Jan 14, 2015 at 10:03 PM
> Subject: Re: Question about kernel interfaces
> To: Siddhartha De <siddhartha.de87@gmail.com>
> Cc: linux-kernel <linux-kernel@vger.kernel.org>
>
>
>> Just wanted to point out something  :-
>>
>> Quoting from makelinux website :-
>> http://www.makelinux.net/books/lkd2/ch17lev1sec8
>>
>> "The sysfs filesystem is currently the place for implementing
>> functionality previously reserved for ioctl() calls on device nodes or
>> the procfs filesystem. These days, the chic thing to do is implement
>> such functionality as sysfs attributes in the appropriate directory.
>> For example, instead of a new ioctl() on a device node, add a sysfs
>> attribute in the driver's sysfs directory. Such an approach avoids the
>> type-unsafe use of obscure ioctl() arguments and the haphazard mess of
>> /proc. "
>
> And is wrong. Certainly rather clueless people had the idea they could
> make ioctl go away using sysfs, and then everyone wrote about it. Anyone
> who actually thought about the problem realised immediately they are not
> semantically equivalent.
>
>> sysfs is the new ioctl
>
> And as was pointed out even then they are not semantically equivalent so
> everyone who was talking about "sysfs being the new ioctl" was basically
> talking out the wrong end.
>
> What was done was to stop filling drivers with ioctls for pieces of
> general information which didn't have a context attached to it or
> sequence. Things like power state, what type it is, what bus it is on
> etc. That avoided having zillions of ioctls but at the cost of memory.
>
>> Taking this idea further , could we also expose driver IOCTL's over
>> the network ?
>>
>> For eg to open the cd rom drive we would be calling the following url :-
>
> You could but why would you make the network visible. If you look at real
> clustered systems they all hide the network. You don't care where it is,
> often you don't even care where the drive is.
>
> eject /dev/cdrom
>
> on such a system lets the kernel figure out who to ask to eject it.
>
> The job of an OS is to abstract details like that. In a clustered OS I
> want to be able to type
>
>         mount mydisk
>
> and I don't care who, where or how it gets mounted so long as it appears.
>
> Alan

Re: Question about kernel interfaces

[Valdis.Kletnieks]

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On Sun, 18 Jan 2015 15:03:55 +0530, Siddhartha De said:

> Let's say you need to call an ioctl from a shell script ( I know its a
> very rare use case but please bear with me ... :) )

There's a *reason* it's very rare...

> So the current way of doing it is probably to write a C program which
> actually calls the ioctl and then call the C program from the shell
> script ...
>
> However if we exposed the IOCTL as a web url we could easily call its
> services by using a simple utility like curl . So in our shell script
> we would probably write :-
>
> curl http://localhost:7000/IOCTL/IOCTL_EJECT?device=/dev/cdrom
>
> and the IOCTL_EJECT ioctl would get called on /dev/cdrom
> that is ioctl ( &handle_to_/dev/cdrom , IOCTL_EJECT , &some_buffer )
> would get called ( by our translator running as a separate program or
> as a service daemon )
>

Why use curl when /usr/bin/eject is almost certainly available?

Can you point at an *actual* case where (a) shell script access even makes
*sense*, and also (b) there *isn't* already a program available for the
shell script to call to issue the ioctl?

Or point at a non-shell language that *doesn't* have already have access to the
ioctl() wrapper that's in whatever libc you have?

I think you're trying to solve a non-problem here.

(For bonus points, instead of EJECT, explain how you form a curl URL
that does TCSETS. Yes, you *do* have to handle *all* the fields of a
struct termios, for both 32 and 64 bit environments....)

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Question about kernel interfaces

[Valdis.Kletnieks at vt.edu]

On Sun, 18 Jan 2015 15:03:55 +0530, Siddhartha De said:

> Let's say you need to call an ioctl from a shell script ( I know its a
> very rare use case but please bear with me ... :) )

There's a *reason* it's very rare...

> So the current way of doing it is probably to write a C program which
> actually calls the ioctl and then call the C program from the shell
> script ...
>
> However if we exposed the IOCTL as a web url we could easily call its
> services by using a simple utility like curl . So in our shell script
> we would probably write :-
>
> curl http://localhost:7000/IOCTL/IOCTL_EJECT?device=/dev/cdrom
>
> and the IOCTL_EJECT ioctl would get called on /dev/cdrom
> that is ioctl ( &handle_to_/dev/cdrom , IOCTL_EJECT , &some_buffer )
> would get called ( by our translator running as a separate program or
> as a service daemon )
>

Why use curl when /usr/bin/eject is almost certainly available?

Can you point at an *actual* case where (a) shell script access even makes
*sense*, and also (b) there *isn't* already a program available for the
shell script to call to issue the ioctl?

Or point at a non-shell language that *doesn't* have already have access to the
ioctl() wrapper that's in whatever libc you have?

I think you're trying to solve a non-problem here.

(For bonus points, instead of EJECT, explain how you form a curl URL
that does TCSETS. Yes, you *do* have to handle *all* the fields of a
struct termios, for both 32 and 64 bit environments....)
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Re: Question about kernel interfaces

[One Thousand Gnomes]

On Sun, 18 Jan 2015 15:03:55 +0530
> Let's say you need to call an ioctl from a shell script ( I know its a
> very rare use case but please bear with me ... :) )
> 
> So the current way of doing it is probably to write a C program which
> actually calls the ioctl and then call the C program from the shell
> script ...

That's how Unix is designed yes. It means that the ioctl internals are
hidden from the scripts and the tools provided can be used instead.

> and the IOCTL_EJECT ioctl would get called on /dev/cdrom
> that is ioctl ( &handle_to_/dev/cdrom , IOCTL_EJECT , &some_buffer )
> would get called ( by our translator running as a separate program or
> as a service daemon )

You can just run "eject". It knows about all the details of doing an
eject.
 
The equivalent of a "library" in shell scripts is a program. Small,
simple tools that do one job and do it right, or at least before GNU got
hold of them 8)

Alan

Re: Question about kernel interfaces

[Siddhartha De]

>(For bonus points, instead of EJECT, explain how you form a curl URL
>that does TCSETS. Yes, you *do* have to handle *all* the fields of a
>struct termios, for both 32 and 64 bit environments....)


I am new to termios programming so please correct me if I am wrong ...
I did a bit of googling and well here's a probable curl url and the
corresponding pseudocode that needs to be in our interpreter


curl http://localhost:7000/IOCTL/TCSETS2?file_descriptor=fd&cflag=something&ispeed=something&ospeed=something

And here's a little pseudocode for our interpreter :-


struct termios2 tio;
// ioctl(fd, TCGETS2, &tio);

// assuming get_from_url is a function which parses the incomming url
and returns the required parameters


cflag=get_from_url (cflag ) ;
ispeed = get_from_url ( ispeed ) ;
ospeed=get_from_url(ospeed)

tio.c_cflag = cflag ;

tio.c_ispeed = ispeed;
tio.c_ospeed = ospeed;
ioctl(fd, TCSETS2, &tio);





Thanking you in anticipation ,

 Yours sincerely ,

  Kernel newbie

On Wed, Jan 21, 2015 at 11:14 PM, One Thousand Gnomes
<gnomes@lxorguk.ukuu.org.uk> wrote:
> On Sun, 18 Jan 2015 15:03:55 +0530
>> Let's say you need to call an ioctl from a shell script ( I know its a
>> very rare use case but please bear with me ... :) )
>>
>> So the current way of doing it is probably to write a C program which
>> actually calls the ioctl and then call the C program from the shell
>> script ...
>
> That's how Unix is designed yes. It means that the ioctl internals are
> hidden from the scripts and the tools provided can be used instead.
>
>> and the IOCTL_EJECT ioctl would get called on /dev/cdrom
>> that is ioctl ( &handle_to_/dev/cdrom , IOCTL_EJECT , &some_buffer )
>> would get called ( by our translator running as a separate program or
>> as a service daemon )
>
> You can just run "eject". It knows about all the details of doing an
> eject.
>
> The equivalent of a "library" in shell scripts is a program. Small,
> simple tools that do one job and do it right, or at least before GNU got
> hold of them 8)
>
> Alan

Question about kernel interfaces

[Siddhartha De]

>(For bonus points, instead of EJECT, explain how you form a curl URL
>that does TCSETS. Yes, you *do* have to handle *all* the fields of a
>struct termios, for both 32 and 64 bit environments....)


I am new to termios programming so please correct me if I am wrong ...
I did a bit of googling and well here's a probable curl url and the
corresponding pseudocode that needs to be in our interpreter


curl http://localhost:7000/IOCTL/TCSETS2?file_descriptor=fd&cflag=something&ispeed=something&ospeed=something

And here's a little pseudocode for our interpreter :-


struct termios2 tio;
// ioctl(fd, TCGETS2, &tio);

// assuming get_from_url is a function which parses the incomming url
and returns the required parameters


cflag=get_from_url (cflag ) ;
ispeed = get_from_url ( ispeed ) ;
ospeed=get_from_url(ospeed)

tio.c_cflag = cflag ;

tio.c_ispeed = ispeed;
tio.c_ospeed = ospeed;
ioctl(fd, TCSETS2, &tio);





Thanking you in anticipation ,

 Yours sincerely ,

  Kernel newbie

On Wed, Jan 21, 2015 at 11:14 PM, One Thousand Gnomes
<gnomes@lxorguk.ukuu.org.uk> wrote:
> On Sun, 18 Jan 2015 15:03:55 +0530
>> Let's say you need to call an ioctl from a shell script ( I know its a
>> very rare use case but please bear with me ... :) )
>>
>> So the current way of doing it is probably to write a C program which
>> actually calls the ioctl and then call the C program from the shell
>> script ...
>
> That's how Unix is designed yes. It means that the ioctl internals are
> hidden from the scripts and the tools provided can be used instead.
>
>> and the IOCTL_EJECT ioctl would get called on /dev/cdrom
>> that is ioctl ( &handle_to_/dev/cdrom , IOCTL_EJECT , &some_buffer )
>> would get called ( by our translator running as a separate program or
>> as a service daemon )
>
> You can just run "eject". It knows about all the details of doing an
> eject.
>
> The equivalent of a "library" in shell scripts is a program. Small,
> simple tools that do one job and do it right, or at least before GNU got
> hold of them 8)
>
> Alan