Re: [Q] How can I transfer data from hard disk to PCI device'smemory

Re: [Q] How can I transfer data from hard disk to PCI device'smemory

[Cho, joon-woo]

Not to PCI device's register, but to PCI device's SDRAM memory.

In detail after I modify kernel, I want to transfer data

from HDD controller's data register (IDE controller case)

to another PCI's SDRAM memory with the help of kernel

( I think Direct I/O(using O_DIRECT flag) )

Is this impossible?


----- Original Message -----
From: "wa moua" <wmatlus@yahoo.com>
To: "Cho, joon-woo" <jwc@core.kaist.ac.kr>
Sent: Friday, August 08, 2003 1:19 AM
Subject: Re: [Q] How can I transfer data from hard disk to PCI
device'smemory


> Are you trying to transfer data from one PCI register
> to another PCI register? Could you please rephrase
> your problem. PCI is a bus not a system storage.
>
> --- "Cho, joon-woo" <jwc@core.kaist.ac.kr> wrote:
> > Thank you for your reply, and I am very pleasant to
> > talk with you. ^^
> >
> > But english is not mother tongue, so I am little
> > confused about your
> > sentence.
> >
> > > The O_DIRECT I/O handling
> > > needs to know about stuff like page reference
> > counts that PCI space
> > > doesn't have lots of older (and some current)
> > hardware has real problems
> > > with PCI PCI transfers.
> >
> > At above sentence, you mean that
> >
> > 'To handle O_DIRECT I/O, stuff like page reference
> > is needed.
> >
> > But some HW(expecially old HW) doesn't have PCI
> > space,
> >
> > so that it needs much additional work to add a
> > PCI-PCI transferring.'
> >
> > Do I understand right?
> >
> >
> > Please reply, thanks.
> >
> >
> >
> > > So its a non trivial project, although doable

[Q] How can I transfer data from hard disk to PCI device's memory

[Cho, joon-woo]

Hello.

I want to transfer data 'directly' from hard disk to some PCI device which
has memory

with the helpf of kernel(file system, device driver).

In above sentence 'directly' means that data does not go through main memory
of host.


So I am analyzing kernel code, but I am so confused because of memory system

complexity (page, buffer, ... ).

I find buffer head structure(struct buffer_head) has b_data pointer
variable.

I think kernel transfer data from HDD to this pointer variable.

Can I map this pointer variable(b_data) to PCI device's memory?


I am very confused because this part is highly related with complex memory
system

(page & buffer).

Please give me some hint. Thanks.

Re: [Q] How can I transfer data from hard disk to PCI device's memory

[Alan Cox]

On Iau, 2003-08-07 at 06:45, Cho, joon-woo wrote:
> Hello.
> 
> I want to transfer data 'directly' from hard disk to some PCI device which
> has memory
> 
> with the helpf of kernel(file system, device driver).

The kernel doesn;t currently support this. The O_DIRECT I/O handling
needs to know about stuff like page reference counts that PCI space
doesn't have lots of older (and some current) hardware has real problems
with PCI PCI transfers.


So its a non trivial project, although doable

Re: [Q] How can I transfer data from hard disk to PCI device'smemory

[Cho, joon-woo]

Thank you for your reply, and I am very pleasant to talk with you. ^^

But english is not mother tongue, so I am little confused about your
sentence.

> The O_DIRECT I/O handling
> needs to know about stuff like page reference counts that PCI space
> doesn't have lots of older (and some current) hardware has real problems
> with PCI PCI transfers.

At above sentence, you mean that

'To handle O_DIRECT I/O, stuff like page reference is needed.

But some HW(expecially old HW) doesn't have PCI space,

so that it needs much additional work to add a PCI-PCI transferring.'

Do I understand right?


Please reply, thanks.



> So its a non trivial project, although doable