From aad6ce38420a0382171262672e4da5d37a69148b Mon Sep 17 00:00:00 2001 From: Mauro Carvalho Chehab Date: Mon, 13 Jan 2014 03:34:23 -0300 Subject: [PATCH] upstream: [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 --- drivers/media/usb/em28xx/em28xx-audio.c | 8 ++++++++ drivers/media/usb/em28xx/em28xx.h | 2 ++ 2 files changed, 10 insertions(+) diff --git a/drivers/media/usb/em28xx/em28xx-audio.c b/drivers/media/usb/em28xx/em28xx-audio.c index 5b2a5e3..5f5cd5d 100644 --- a/drivers/media/usb/em28xx/em28xx-audio.c +++ b/drivers/media/usb/em28xx/em28xx-audio.c @@ -304,7 +304,12 @@ 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; @@ -812,6 +817,9 @@ 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, diff --git a/drivers/media/usb/em28xx/em28xx.h b/drivers/media/usb/em28xx/em28xx.h index 18dd79f..90e7cec 100644 --- a/drivers/media/usb/em28xx/em28xx.h +++ b/drivers/media/usb/em28xx/em28xx.h @@ -506,6 +506,8 @@ struct em28xx_audio { unsigned int hwptr_done_capture; struct snd_card *sndcard; + size_t period; + int users; spinlock_t slock; }; -- 2.7.4