From: Jyri Sarha <jsarha@ti.com>
To: Dan Carpenter <dan.carpenter@oracle.com>
Cc: "Ujfalusi, Peter" <peter.ujfalusi@ti.com>,
alsa-devel@alsa-project.org, Mark Brown <broonie@kernel.org>
Subject: Re: ASoC: davinci-mcasp: Set rule constraints if implicit BCLK divider is used
Date: Mon, 13 Apr 2015 14:39:06 +0300 [thread overview]
Message-ID: <552BAADA.5060401@ti.com> (raw)
In-Reply-To: <20150410093336.GA5779@mwanda>
On 04/10/15 12:33, Dan Carpenter wrote:
> Hello Jyri Sarha,
>
> The patch a75a053f1eef: "ASoC: davinci-mcasp: Set rule constraints if
> implicit BCLK divider is used" from Mar 20, 2015, leads to the
> following Sparse warning:
>
> sound/soc/davinci/davinci-mcasp.c:1098:45:
> warning: Variable length array is used.
>
> sound/soc/davinci/davinci-mcasp.c
> 1088 static int davinci_mcasp_hw_rule_channels(struct snd_pcm_hw_params *params,
> 1089 struct snd_pcm_hw_rule *rule)
> 1090 {
> 1091 struct davinci_mcasp_ruledata *rd = rule->private;
> 1092 struct snd_interval *ci =
> 1093 hw_param_interval(params, SNDRV_PCM_HW_PARAM_CHANNELS);
> 1094 int sbits = params_width(params);
> 1095 int rate = params_rate(params);
> 1096 int max_chan_per_wire = rd->mcasp->tdm_slots < ci->max ?
> 1097 rd->mcasp->tdm_slots : ci->max;
> 1098 unsigned int list[ci->max - ci->min + 1];
> ^^^^^^^^^^^^^^^^^^^^^
> I wasnt able to determine where these values are capped. The worry is
> that the kernel only has an 8k stack so if they are too high it could
> oops. I think these values can come from the user in
> snd_pcm_hw_params_user() but I'm an newbie to the code and I didn't
> see where the limits were enforced.
>
In theory the ci->max should never be more than 512, because
static struct snd_soc_dai_driver davinci_mcasp_dai[] = {
...
.channels_max = 32 * 16,
should limit the maximum allowed channel index. Normally this value
should be way smaller.
However, since there is considerable amount of code involved it is hard
to be produce a proof of that. I could add a hard max limit of 512 - or
even 128 - to the list size. The cases when the list size would need to
be even close 128 are quite theoretical.
Best regards,
Jyri
> 1099 int c1, c, count = 0;
> 1100
> 1101 for (c1 = ci->min; c1 <= max_chan_per_wire; c1++) {
> 1102 uint bclk_freq = c1*sbits*rate;
> 1103 int ppm;
>
>
> regards,
> dan carpenter
>
next prev parent reply other threads:[~2015-04-13 11:39 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-10 9:33 ASoC: davinci-mcasp: Set rule constraints if implicit BCLK divider is used Dan Carpenter
2015-04-13 11:39 ` Jyri Sarha [this message]
2015-04-13 12:16 ` Dan Carpenter
2015-04-13 13:32 ` Jyri Sarha
2015-04-13 13:58 ` Dan Carpenter
2015-04-13 14:22 ` Takashi Iwai
-- strict thread matches above, loose matches on Subject: below --
2015-03-27 6:20 Dan Carpenter
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