From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jyri Sarha Subject: Re: ASoC: davinci-mcasp: Set rule constraints if implicit BCLK divider is used Date: Mon, 13 Apr 2015 14:39:06 +0300 Message-ID: <552BAADA.5060401@ti.com> References: <20150410093336.GA5779@mwanda> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: Received: from bear.ext.ti.com (bear.ext.ti.com [192.94.94.41]) by alsa0.perex.cz (Postfix) with ESMTP id 27C3B261AD0 for ; Mon, 13 Apr 2015 13:39:11 +0200 (CEST) In-Reply-To: <20150410093336.GA5779@mwanda> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: alsa-devel-bounces@alsa-project.org To: Dan Carpenter Cc: "Ujfalusi, Peter" , alsa-devel@alsa-project.org, Mark Brown List-Id: alsa-devel@alsa-project.org 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 >