linux-kernel - Re: [Alsa-devel] [PATCH] alsa: correct nonsensical sysfs device symlinks

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Message-ID: <20070126180457.GA29543@kroah.com>
Date:	Fri, 26 Jan 2007 10:04:57 -0800
From:	Greg KH <greg@...ah.com>
To:	Takashi Iwai <tiwai@...e.de>
Cc:	xiphmont@...h.org, Pierre Ossman <drzeus@...eus.cx>,
	fedora-desktop-list@...hat.com, alsa-devel@...a-project.org,
	jrb@...hat.com, linux-kernel@...r.kernel.org, mclasen@...hat.com,
	Lennart Poettering <lennart@...ttering.net>, perex@...e.cz
Subject: Re: [Alsa-devel] [PATCH] alsa: correct nonsensical sysfs device symlinks

On Fri, Jan 26, 2007 at 12:40:31PM +0100, Takashi Iwai wrote:
> At Fri, 26 Jan 2007 05:53:36 -0500,
> xiphmont@...h.org wrote:
> > 
> > On 1/25/07, Greg KH <greg@...ah.com> wrote:
> > 
> > > Is there anything else left to fix?
> > 
> > Once that testing is done, no.  But don't trust the two patches I sent
> > yet, I'll resumbit the patch resulting from more thorough testing in a
> > few hours (much thanks to Takashi for giving me the parent device
> > feedback I was trolling for).
> 
> After rechecking the current code regarding this sysfs change at last
> night, I found out that it's more broken for some devices like
> sound/arm/*.  They refer to card->dev to obtain the device for memory
> allocation, etc, and passing card* object will screw them up.
> 
> The below is my current fix.  Hoepfully all evils got away now...  and
> thanks for Monty for heading up this issue!
> 
> 
> Takashi
> 
> ====
> [PATCH] ALSA: Fix sysfs breakage
> 
> The recent change for a new sysfs tree with card* object breaks the
> /sys/class/sound tree if CONFIG_SYSFS_DEPRECATED is enabled.
> The device in each entry doesn't point the correct device object:
> 
>   /sys/class/sound
>   ...
>   |-- pcmC0D0c
>   |   |-- dev
>   |   |-- device -> ../../../class/sound/card0
>   |   |-- pcm_class
>   |   |-- power
>   |   |   `-- wakeup
>   |   |-- subsystem -> ../../../class/sound
>   |   `-- uevent
> 
> Also, this change breaks some drivers (like sound/arm/*) referring
> card->dev directly to obtain the device object for memory handling.
> 
> This patch reverts the semantics of card->dev to the former version,
> which points to a real device object.  The card* object is stored in a
> new card->card_dev field, instead.  The device parent is chosen either
> card->dev or card->card_dev according to CONFIG_SYSFS_DEPRECATED to
> keep the tree compatibility.
> Also, card* isn't created if CONFIG_SYSFS_DEPRECATED is enabled.  The
> reason of card* object is a root of all beloing devices, and it makes
> little sense if each sound device points to the real device object
> directly.
> 
> Signed-off-by: Takashi Iwai <tiwai@...e.de>

Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

Thanks for working on tracking this down, sorry I forgot all about this
when doing this original conversion.

greg k-h
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