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