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

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Date:	Thu, 19 Dec 2013 17:06:23 +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 15:54:59 +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?

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.


Takashi


> Although this implementation may not be portable, the alternative
> breaks audio on anything using the AB8500 CODEC, which is a much
> greater evil. Besides, this driver will never run on anything
> else.
> 
> Cc: Takashi Iwai <tiwai@...e.de>
> Signed-off-by: Lee Jones <lee.jones@...aro.org>
> ---
>  sound/soc/codecs/ab8500-codec.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/sound/soc/codecs/ab8500-codec.c b/sound/soc/codecs/ab8500-codec.c
> index 1ad92cb..51ae3e9 100644
> --- a/sound/soc/codecs/ab8500-codec.c
> +++ b/sound/soc/codecs/ab8500-codec.c
> @@ -2322,7 +2322,7 @@ static int ab8500_codec_set_dai_tdm_slot(struct snd_soc_dai *dai,
>  		slot = ffs(tx_mask);
>  		snd_soc_update_bits(codec, AB8500_DASLOTCONF1, mask, slot);
>  		snd_soc_update_bits(codec, AB8500_DASLOTCONF3, mask, slot);
> -		slot = fls(tx_mask);
> +		slot = find_next_bit((unsigned long *)&tx_mask, 32, slot + 1);
>  		snd_soc_update_bits(codec, AB8500_DASLOTCONF2, mask, slot);
>  		snd_soc_update_bits(codec, AB8500_DASLOTCONF4, mask, slot);
>  		break;
> @@ -2364,7 +2364,7 @@ static int ab8500_codec_set_dai_tdm_slot(struct snd_soc_dai *dai,
>  				AB8500_ADSLOTSEL(slot),
>  				AB8500_MASK_SLOT(slot),
>  				AB8500_ADSLOTSELX_AD_OUT_TO_SLOT(AB8500_AD_OUT3, slot));
> -		slot = fls(rx_mask);
> +		slot = find_next_bit((unsigned long *)&rx_mask, 32, slot + 1);
>  		snd_soc_update_bits(codec,
>  				AB8500_ADSLOTSEL(slot),
>  				AB8500_MASK_SLOT(slot),
> -- 
> 1.8.3.2
> 
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