On 09/21/15 12:37, Russell King - ARM Linux wrote:
On Fri, Sep 18, 2015 at 02:06:39PM +0300, Jyri Sarha wrote:
Add IEC958 channel status helper that gets the audio properties from
snd_pcm_hw_params instead of snd_pcm_runtime. This is needed to
produce the channel status bits already in audio stream configuration
phase.
What is the reason for doing this early?
After some thinking, there is no good reason. It makes the codec bit
more complicated, but that is not a good reason. I'll change that and
use the prepare callback.
This patch can be dropped.
ALSA documentation (which may be out of date) says that the hw_params
callback can be called multiple times during stream setup. Do we want
to be repeatedly programming the HDMI infoframe with different settings,
potentially confusing the attached device, or would it be better to do
it slightly later (in the prepare callback) after the parameters have
been fully negotiated?
If it is possible that hw_params() can be called multiple times, at
least it does not happen very often. I wonder if it would ever happen
again after a successful hw_params() call. But there is no downside in
using prepare callback. I was just too much following the way ASoC
codecs usually do the thing by writing everything to iron as the
callbacks come in.
Best regards,
Jyri
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