Re: [PATCH 2/3 v2] ALSA: usb-audio: avoid setting of sample rate multiple times on bus

From: Jiada Wang
Date: Thu Dec 01 2016 - 02:08:06 EST


Hi Takashi

On 11/30/2016 05:51 PM, Takashi Iwai wrote:
On Wed, 30 Nov 2016 08:59:22 +0100,
Jiada Wang wrote:

From: Daniel Girnus <dgirnus@xxxxxxxxxxxxxx>

ALSA usually calls the prepare function twice before starting the playback:
1. On hw_params call from userland and
2. internally when starting the stream.
Some device are not able to manage this and they will stop playback
if the sample rate will be configured several times over USB protocol.

Signed-off-by: Jens Lorenz <jlorenz@xxxxxxxxxxxxxx>
Signed-off-by: Jiada Wang <jiada_wang@xxxxxxxxxx>

The sign-off from Daniel seems missing?

The code change looks OK, but it'd be nice to mention in the changelog
that, after this patch, snd_usb_init_sample_rate() is still called
properly whenever the parameter is changed since ep->need_setup_ep is
set in snd_hsb_hw_params().

I will add missing sign-off and related information in changelog in v2

Thanks,
Jiada

thanks,

Takashi

---
sound/usb/pcm.c | 21 +++++++++++----------
1 file changed, 11 insertions(+), 10 deletions(-)

diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
index 44d178e..a522c9a 100644
--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -806,17 +806,18 @@ static int snd_usb_pcm_prepare(struct snd_pcm_substream *substream)
if (ret < 0)
goto unlock;

- iface = usb_ifnum_to_if(subs->dev, subs->cur_audiofmt->iface);
- alts = &iface->altsetting[subs->cur_audiofmt->altset_idx];
- ret = snd_usb_init_sample_rate(subs->stream->chip,
- subs->cur_audiofmt->iface,
- alts,
- subs->cur_audiofmt,
- subs->cur_rate);
- if (ret < 0)
- goto unlock;
-
if (subs->need_setup_ep) {
+
+ iface = usb_ifnum_to_if(subs->dev, subs->cur_audiofmt->iface);
+ alts = &iface->altsetting[subs->cur_audiofmt->altset_idx];
+ ret = snd_usb_init_sample_rate(subs->stream->chip,
+ subs->cur_audiofmt->iface,
+ alts,
+ subs->cur_audiofmt,
+ subs->cur_rate);
+ if (ret < 0)
+ goto unlock;
+
ret = configure_endpoint(subs);
if (ret < 0)
goto unlock;
--
2.9.3