linux-kernel - Re: [PATCH 02/11] ASoC: ab8500: Revert back to find_next

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Message-ID: <s5hzjnwrbq2.wl%tiwai@suse.de>
Date:	Thu, 19 Dec 2013 18:29:09 +0100
From:	Takashi Iwai <tiwai@...e.de>
To:	Lee Jones <lee.jones@...aro.org>
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linus.walleij@...aro.org, broonie@...nel.org,
	alsa-devel@...a-project.org
Subject: Re: [PATCH 02/11] ASoC: ab8500: Revert back to find_next_bit()

At Thu, 19 Dec 2013 16:48:24 +0000,
Lee Jones wrote:
> 
> > > Commit '166a34d ASoC: ab8500: Fix invalid cast to long pointer'
> > > rather carelessly converts find_next_bit() to fls() (find last
> > > bit set), which are not the same.
> > 
> > Does it break on the real machines?
> 
> It does, that's how I found the bug.
> 
> > fls() behaves differently from find_next_bit(), of course, but in this
> > case, it should work same in the end, since there are at most two
> > bits.
> 
> Unfortunately it doesn't work at all. This patch brings audio back to
> a working state. It took me the best part of a day to track down the
> issue. :(

Hmm, then isn't the original code rather buggy?

Check the values set there by ffs(), fls() and the original
find_next_bit(), especially whether find_next_bit() gives a valid
value fitting with the mask bits.


Takashi
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