AW: USB kernel driver

AW: USB kernel driver

[jochen]

> > jochen@mades.net writes:
> > 
> > Hi,
> > 
> > > can somebody tell me if it is possible to integrate an USB kernel
> > > driver (f. ex. linux-2.6.0\drivers\usb) into GRUB2 to access USB
> > > devices?
> > >
> > > If possible, it would be great if somebody could tell me what basic
> > > steps I have to do.
> > 
> > I don't think it is possible.  Linux has multitasking, interrupt
> > handing, a drive framework including the required bus drives, etc.
> > 
> > For GRUB we have to write our own drivers, I think.  And besides
that,
> > I don't think it is nice to maintain the glue code.
> 

First of all thanks for your comments!

So it seems to me the only way is to write it our own. Or are there any
more ideas where to "borrow" code from?

Writing a own GRUB USB driver seems to be a complicated task, starting
with the three standards UHCI, EHCI and OHCI.

Furthermore I have no experience with GRUB drivers! Is there any
documentation besides the source code?

Jochen

Re: AW: USB kernel driver

[Yoshinori K. Okuji]

On Wednesday 19 October 2005 08:07 am, jochen@mades.net wrote:
> So it seems to me the only way is to write it our own. Or are there any
> more ideas where to "borrow" code from?

You can refer to other code for a reference purpose, but it is important to 
keep it in mind that the operating environment of GRUB is fundamentally 
different from OS. Since OS wants complete control of hardware, it usually 
reconfigures many parameters and makes use of hardware interrupts for a 
performance reason, while GRUB tries to keep an underlying system as intact 
as possible for safety. So, in GRUB, interrupt-driven code is inappropriate, 
and a polling-based approach is often nicer.

> Writing a own GRUB USB driver seems to be a complicated task, starting
> with the three standards UHCI, EHCI and OHCI.

It is complicated if you attempt to obtain a perfect thing from the beginning. 
To start a project, the best way is, IMO, to start from what you really need 
yourself. For example, you should have a system which has one of the USB 
systems, but not all of them. So I'd recommend you implementing "just work 
for me" code as a first step.

> Furthermore I have no experience with GRUB drivers! Is there any
> documentation besides the source code?

No, but you don't need it, since the environment is quite simple. GRUB is just 
a single task, and there is little concern about security or performance.

Okuji

AW: USB kernel driver

[jochen]

Hi,

because of not knowing the GRUB 2 architecture very well so far, it would
be nice if you could give me some tipps about
- what does the GRUB development enviroment looks like (means how does
your test PCs look like, how to put updates on the test PC an so on)
- ways to debug my code
- where in source code should I place my test driver

Thx
Jochen

 --- Ursprüngliche Nachricht ---
Datum: 20.10.2005 01:37
Von: The development of GRUB 2 <grub-devel@gnu.org>
An: The development of GRUB 2 <grub-devel@gnu.org>
Betreff: Re: AW: USB kernel driver

> On Wednesday 19 October 2005 08:07 am, jochen@mades.net wrote:
> > So it seems to me the only way is to write it our own. Or are there
any
> > more ideas where to "borrow" code from?
>
> You can refer to other code for a reference purpose, but it is important
to
> keep it in mind that the operating environment of GRUB is fundamentally

> different from OS. Since OS wants complete control of hardware, it
usually
> reconfigures many parameters and makes use of hardware interrupts for a

> performance reason, while GRUB tries to keep an underlying system as
intact
> as possible for safety. So, in GRUB, interrupt-driven code is
inappropriate,
> and a polling-based approach is often nicer.
>
> > Writing a own GRUB USB driver seems to be a complicated task,
starting
> > with the three standards UHCI, EHCI and OHCI.
>
> It is complicated if you attempt to obtain a perfect thing from the
beginning.
> To start a project, the best way is, IMO, to start from what you really
need
> yourself. For example, you should have a system which has one of the USB

> systems, but not all of them. So I'd recommend you implementing "just
work
> for me" code as a first step.
>
> > Furthermore I have no experience with GRUB drivers! Is there any
> > documentation besides the source code?
>
> No, but you don't need it, since the environment is quite simple. GRUB
is just
> a single task, and there is little concern about security or
performance.
>
> Okuji
>
>
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