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

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Date:	Sun, 25 May 2008 15:40:35 +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


> > Why are you so fixated on special-casing the single character '/'?
> 
> It is not the "/" character. It is the directory separator. Just  
> happened to be "/" on Unix operating systems. You are really missing  
> my point here. The kernel should not be involved in enforcing this  
> kind of namespaces.

Why are you thinking of it as namespaces then? It isn't. The "firmware
key" lives in a flat namespace where each key is an arbitrary
nul-terminated string.

> Look at the device nodes. The kernel has mouse0 for example and udev  
> will translate this into /dev/input/mouse0. Nobody expects the kernel  
> to use input/mouse0 and actually you even can't do that at all since  
> the device model forbids "/" as bus id. Same applies for the firmware  
> filenames.

No, it doesn't.

> Also at some point we might change the actual implementation of  
> request_firmware() to allow running multiple request_firmware() at the  
> same time to improve the init time of devices (if that makes sense).  
> In that case the filename would become a kobject and then the  
> directory separator would become illegal.

There's no need to think of it that way. Look at a uevent now:

UEVENT[1211722721.323011] add      /devices/pci0001:10/0001:10:12.0/ssb0:0/firmware/ssb0:0 (firmware)
ACTION=add
DEVPATH=/devices/pci0001:10/0001:10:12.0/ssb0:0/firmware/ssb0:0
SUBSYSTEM=firmware
FIRMWARE=b43/b0g0bsinitvals5.fw
TIMEOUT=60
SEQNUM=1376


The "firmware key" is contained in the FIRMWARE environment variable. If
you want to allow loading multiple firmwares at the same time, you
wouldn't have to make the key part of the device name, you would only
have to add a unique ID to the firmware device name, say


UEVENT[1211722721.323011] add      /devices/pci0001:10/0001:10:12.0/ssb0:0/firmware/ssb0:0-1234 (firmware)
ACTION=add
DEVPATH=/devices/pci0001:10/0001:10:12.0/ssb0:0/firmware/ssb0:0-1234
SUBSYSTEM=firmware
FIRMWARE=b43/b0g0bsinitvals5.fw
TIMEOUT=60
SEQNUM=1376

johannes

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