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Re: AW: USB kernel driver

From: Yoshinori K. Okuji
Subject: Re: AW: USB kernel driver
Date: Thu, 20 Oct 2005 01:37:35 +0200
User-agent: KMail/1.7.2

On Wednesday 19 October 2005 08:07 am, address@hidden 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.


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