linux-kernel - Re: firmware loading interface

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Message-ID: <4B012FFC.1080600@csldevices.co.uk>
Date:	Mon, 16 Nov 2009 10:57:00 +0000
From:	Philip Downer <phil@...devices.co.uk>
To:	Arnd Bergmann <arnd@...db.de>
CC:	linux-kernel@...r.kernel.org
Subject: Re: firmware loading interface

Arnd Bergmann wrote:
> On Friday 13 November 2009, Philip Downer wrote:
>   
>> However our device will have flash to store the firmware in and, whilst
>> it looks as though it would be possible for us to use request_firmware
>> to provide occasional firmware upgrades from userspace, I can't find any
>> reference as to whether this is an accepted method for doing so. Could
>> someone please confirm for me whether or not it's a good idea to use
>> request_firmware for this, or perhaps point me at another standard
>> method for doing firmware updates from userspace?
>>     
>
> The idea of request_firmware is that it helps you load the firmware
> into the device at initialization time so you can use it directly,
> without making the firmware blob a part of the kernel driver.
>
> If I understand you correctly, you never need a firmware in user space
> in order to use the device, but only for flashing a new version into
> the nonvolatile memory.
>   

Thats correct.

> The easiest way to do that would be an ioctl operation, if you are
> implementing a character or block device interface anyway. Just load
> the firmware into the RAM of a user application and call an ioctl
> with the pointer to the firmware as an argument, but don't use
> a data structure with a pointer in it, which would mess up 32 bit
> compatibility operation.

Thank you for this suggestion and for the warning about 32bit, we are in 
fact implementing a character device and could use this method.

Thanks,

Philip Downer
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