linux-kernel - Re: [PATCH 01/18] Altera FPGA firmware download module.

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Message-ID: <4D1DC2DD.6050400@infradead.org>
Date:	Fri, 31 Dec 2010 09:47:41 -0200
From:	Mauro Carvalho Chehab <mchehab@...radead.org>
To:	Laurent Pinchart <laurent.pinchart@...asonboard.com>
CC:	"Igor M. Liplianin" <liplianin@...by>, linux-media@...r.kernel.org,
	linux-kernel@...r.kernel.org, aospan@...up.ru
Subject: Re: [PATCH 01/18] Altera FPGA firmware download module.

Em 31-12-2010 09:30, Laurent Pinchart escreveu:
> Hi Mauro,
> 
> On Friday 31 December 2010 12:27:38 Mauro Carvalho Chehab wrote:
>> Em 31-12-2010 09:12, Laurent Pinchart escreveu:
>>> Hi Igor,
>>>
>>> On Friday 31 December 2010 06:26:31 Igor M. Liplianin wrote:
>>>> It uses STAPL files and programs Altera FPGA through JTAG.
>>>> Interface to JTAG must be provided from main device module,
>>>> for example through cx23885 GPIO.
>>>
>>> It might be a bit late for this comment (sorry for not having noticed the
>>> patch set earlier), but...
>>>
>>> Do we really need a complete JTAG implementation in the kernel ? Wouldn't
>>> it better to handle this in userspace with a tiny kernel driver to
>>> access the JTAG signals ?
>>
>> Laurent,
>>
>> Igor already explained it. From what I understood, the device he is
>> working has a firmware that needs to be loaded via JTAG/FPGA.
> 
> I understand this. However, a complete JTAG state machine in the kernel, plus 
> an Altera firmware parser, seems to be a lot of code that could live in 
> userspace.

Moving it to userspace would mean a kernel driver that would depend on an
userspace daemon^Wfirmware loader to work. I would NAK such designs.

The way it is is fine from my POV.

>> Actually, I liked the idea, as the FPGA programming driver could be
>> useful if other drivers have similar usecases.
> 
> If I understand it correctly the driver assumes the firmware is in an Altera 
> proprietary format. If we really want JTAG code in the kernel we should at 
> least split the file parser and the TAP access code.
> 

Agreed, but I don't think this would be a good reason to block the code merge
for .38.

Cheers,
Mauro
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