Messages in this thread | | | Date | Tue, 6 Feb 2024 16:08:36 -0800 | Subject | Re: [PATCH v13 32/53] ALSA: usb-audio: Check for support for requested audio format | From | Wesley Cheng <> |
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Hi Takashi,
On 2/6/2024 5:12 AM, Takashi Iwai wrote: > On Sat, 03 Feb 2024 03:36:24 +0100, > Wesley Cheng wrote: >> >> Allow for checks on a specific USB audio device to see if a requested PCM >> format is supported. This is needed for support when playback is >> initiated by the ASoC USB backend path. >> >> Signed-off-by: Wesley Cheng <quic_wcheng@quicinc.com> > > Just cosmetic: > >> +struct snd_usb_stream *snd_usb_find_suppported_substream(int card_idx, >> + struct snd_pcm_hw_params *params, int direction) >> +{ >> + struct snd_usb_audio *chip; >> + struct snd_usb_substream *subs; >> + struct snd_usb_stream *as; >> + const struct audioformat *fmt; >> + >> + /* >> + * Register mutex is held when populating and clearing usb_chip >> + * array. >> + */ >> + mutex_lock(®ister_mutex); >> + chip = usb_chip[card_idx]; >> + if (!chip) { >> + mutex_unlock(®ister_mutex); >> + return NULL; >> + } >> + >> + if (enable[card_idx]) { >> + list_for_each_entry(as, &chip->pcm_list, list) { >> + subs = &as->substream[direction]; >> + fmt = snd_usb_find_substream_format(subs, params); >> + if (fmt) { >> + mutex_unlock(®ister_mutex); >> + return as; >> + } >> + } >> + } >> + mutex_unlock(®ister_mutex); > > I prefer having the single lock/unlock call pair, e.g. > > struct snd_usb_stream *as, *ret; > > ret = NULL; > mutex_lock(®ister_mutex); > chip = usb_chip[card_idx]; > if (chip && enable[card_idx]) { > list_for_each_entry(as, &chip->pcm_list, list) { > subs = &as->substream[direction]; > if (snd_usb_find_substream_format(subs, params)) { > ret = as; > break; > } > } > } > mutex_unlock(®ister_mutex); > return ret; > } > > In this case, we shouldn't reuse "as" for the return value since it > can be non-NULL after the loop end. > > Sure will do, thanks for taking a look.
Thanks Wesley Cheng
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