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[media] em28xx: adjust period size at runtime 

While the current hardcoded period is ok for the current values,
we may latter change the driver to work with different bit rates
or with different latencies than 64ms.

So, adust the period size at runtime.

Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>
This commit is contained in:
Mauro Carvalho Chehab 2014-01-13 03:34:23 -03:00
parent ebbfbc2006
commit a02b9c238b
2 changed files with 10 additions and 0 deletions
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8
drivers/media/usb/em28xx/em28xx-audio.c
View File

@ -293,7 +293,12 @@ static int snd_em28xx_capture_open(struct snd_pcm_substream *substream)
mutex_unlock(&dev->lock);
}
/* Dynamically adjust the period size */
snd_pcm_hw_constraint_integer(runtime, SNDRV_PCM_HW_PARAM_PERIODS);
snd_pcm_hw_constraint_minmax(runtime, SNDRV_PCM_HW_PARAM_PERIOD_BYTES,
dev->adev.period * 95 / 100,
dev->adev.period * 105 / 100);
dev->adev.capture_pcm_substream = substream;
return 0;
@ -803,6 +808,9 @@ static int em28xx_audio_urb_init(struct em28xx *dev)
em28xx_info("Number of URBs: %d, with %d packets and %d size",
num_urb, npackets, urb_size);
/* Estimate the bytes per period */
dev->adev.period = urb_size * npackets;
/* Allocate space to store the number of URBs to be used */
dev->adev.transfer_buffer = kcalloc(num_urb,

2
drivers/media/usb/em28xx/em28xx.h
View File

@ -505,6 +505,8 @@ struct em28xx_audio {
unsigned int hwptr_done_capture;
struct snd_card *sndcard;
size_t period;
int users;
spinlock_t slock;
};