linux-kernel - Re: [PATCH] firmware: avoiding multiple replication for same firmware file

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Date:	Fri, 01 Aug 2008 21:04:28 +0100
From:	David Woodhouse <dwmw2@...radead.org>
To:	Jaswinder Singh <jaswinder@...radead.org>
Cc:	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] firmware: avoiding multiple replication for same
	firmware file

On Fri, 2008-08-01 at 11:30 +0530, Jaswinder Singh wrote:
> Now when request_firmware will be called it will check whether firmware
> is already allocated or not. If already allocated then it provide handle
> of old firmware handle and increase count of firmware.
> 
> release_firmware will decrease count of firmware, if count is one only then
> firmware will be release.

I like this. It means that when you have multiple similar devices, you
only need one copy of the firmware in memory for _all_ of them. Because
we've now made fw->data constant, we know it's safe to share them now.

I wonder if we should change the implementation of 'built-in firmware'
to use your new implementation -- just set the use count on the built-in
firmware to 1 when we start up, and then it should never go away.

Unless we're _really_ clever with linker tricks it would mean we'd have
an init function which takes the built-in stuff and builds it into the
linked list, but I think that might be worth the runtime simplification.

-- 
David Woodhouse                            Open Source Technology Centre
David.Woodhouse@...el.com                              Intel Corporation

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