linux-kernel - Re: [PATCH 2/3] firmware: Add CONFIG_BUILTIN

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Message-Id: <1211716784.17151.19.camel@johannes.berg>
Date:	Sun, 25 May 2008 13:59:44 +0200
From:	Johannes Berg <johannes@...solutions.net>
To:	Marcel Holtmann <marcel@...tmann.org>
Cc:	David Woodhouse <dwmw2@...radead.org>,
	Sam Ravnborg <sam@...nborg.org>, linux-kernel@...r.kernel.org,
	aoliva@...hat.com, alan@...rguk.ukuu.org.uk,
	Abhay Salunke <Abhay_Salunke@...l.com>, kay.sievers@...y.org,
	Takashi Iwai <tiwai@...e.de>, Michael Buesch <mb@...sch.de>
Subject: Re: [PATCH 2/3] firmware: Add CONFIG_BUILTIN_FIRMWARE option

Marcel,

> The kernel should not in any case have knowledge about directories or  
> subdirectories where the firmware files are stored. That is fully  
> irrelevant for the kernel.

Exactly my point! Hence, the kernel just gives it an arbitrary name. The
fact that userspace uses this as a filename could be regarded as a bug,
but it works fine. Therefore, the kernel simply assigns an arbitrary,
NULL-terminated string as the name. It happens to include a / because it
is convenient with the current userspace implementation, but that's mere
detail, the ABI/API here is to allow any arbitrary names.

> Especially with the case of built-in firmwares now, it because more  
> important to do it right. The one reason why we have to handover the  
> struct device to request_firmware() is that we can give the helper  
> script full access to the device and driver information of the caller.  
> Hence adding for example b43/ as prefix simply duplicates everything  
> since the struct device has a link to the driver that is requesting a  
> firmware file.

But that doesn't matter at all! Dave's work to build firmware files into
the kernel will simply result in an entry in the kernel firmware table
that has a '.name = "b43/pcm5.fw"', nothing needs to know that b43 is a
module name, in fact, it could very well be 'broadcom wlan/pcm5.fw' as
well.

> That is not what I am proposing. What I am proposing is that we do  
> this the right way. Meaning that we fix udev to do the namespacing. I  
> am working on a way to have this change in a backward compatible way.

That will introduce a "flag-day" where you have to upgrade userspace
with the kernel, and vice versa, OR userspace will have to guess. Not a
good solution either.

Why are you so fixated on special-casing the single character '/'?

johannes

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