[sw-dev] SBI extension proposal v2

[mick@ics.forth.gr (Nick Kossifidis)]

???? 2018-11-10 21:39, Luke Kenneth Casson Leighton ??????:
> ---
> crowd-funded eco-conscious hardware: https://www.crowdsupply.com/eoma68
> 
> On Sat, Nov 10, 2018 at 5:59 PM Nick Kossifidis <mick@ics.forth.gr> 
> wrote:
>> 
>> ???? 2018-11-10 19:47, Luke Kenneth Casson Leighton ??????:
>> > On Sat, Nov 10, 2018 at 5:42 PM Olof Johansson <olof@lixom.net> wrote:
>> >
>> >> The case of console is in this case pretty simple: It's intended for
>> >> early boot for very simplistic environments (before the rest of the
>> >> kernel is up, etc). Keeping the SBI console around beyond early boot,
>> >> and somehow trying to optimize for it for those use cases is a
>> >> misdirected effort; that's what native drivers are for.
>> >
>> >  spike (which is only around 7,000 lines of code) doesn't have native
>> > drivers, and qemu is too heavy-duty to consider adding custom
>> > extensions and experimental research onto.
>> >
>> >  with nothing in spike *other* than the serial console, it's the only
>> > way in and out.
>> >
>> >  l.
>> 
>> Anything more than a main/debug console is too much for the SBI, its
>> goal is to be used early on in the boot process until the OS or the
>> bare metal app takes control.
> 
>  nooo, that's just _one_ use to which it's being put.
> 
>> Having multiple serial lines through
>> the SBI for things like PPP, UPS, virtual consoles and all the stuff
>> you mentioned is out of scope.
> 
>  why?
> 

Because the firmware is meant to be something minimal, not to replace 
the
OS. Let me ask you this, if you want to change UART speed or settings in
general would you also ask for an SBI call for that ? What's coming up
next ? Adding networking support for example ? Where do you put the 
barrier
on firmware's complexity / scope ?

>> Boot an OS and use the standard UART
>> drivers for accessing the serial lines. If there are no drivers
>> or support on spike, it's open source !
> 
>  this is a common misconception that "because it's open source anyone
> can do what they want".  code costs money.  servers to host code cost
> money.  answering the emails where people expect "free" support
> because you're hosting the only public version of that server costs
> money.
> 

Even if we decide that the SBI gets extended for accessing different
serial lines, someone will have to write code for that e.g. on BBL or on
OpenSBI, coreboot etc. If we follow your logic, maintaining, hosting
and supporting this also costs money. So what's the point here ? That
it's easier to implement it there for everyone than write a UART driver
for spike ?

By the way spike is an ISA simulator, I don't see why it should emulate
UART ports, last time I checked it didn't, so someone will need to write
code for that, more money ! You can use QEMU for that where you can have
as many UARTs as you want and the drivers for them are already available
for you.

>  i'm an ethical libre developer: i can't go footing the bill for other
> people to sponge off my efforts all the time, i've had 20 years of
> people doing that and i'm f*****g well not putting up with it on this
> project.
> 
>  so no, mick, sorry, not buying the argument "it's open source".
> 
> l.

Don't assume you are the only one.

Regards,
Nick