sound: Report actual vchanrate and vchanformat in sysctl

[christos]

Summary

Sponsored by: The FreeBSD Foundation
MFC after: 1 week

[dev_submerge.ch]

sys/dev/sound/pcm/vchan.c

531–532

Since *vchanrate and c->speed can have different values, we should update *vchanrate even when c->speed is unchanged. Otherwise this results in confusing behavior if the user wants to set the sample rate that the channel already is setup with.

635–636

Same as above, regarding *vchanformat instead of *vchanrate.

[christos]

Address comments.

[christos]

Fix to work properly with D47917.

[dev_submerge.ch]

Aren't vchanrate and vchanformat now completely disconnected from the actual parameters of the primary channel, until a vchan is opened? This would mean there's no useful feedback for the user until a channel is opened, at which point the parameters could suddenly change to something different?

[christos]

In D48435#1108253, @dev_submerge.ch wrote:

Aren't vchanrate and vchanformat now completely disconnected from the actual parameters of the primary channel, until a vchan is opened?

Until a vchan is opened not really, because this code is executed only through the sysctl interface. I do agree however, that it's better to assign these values to the primary channel parameters instead, since the chn_reset() might assign something different than what we requested, in which case vchanrate/vchanformat are inconsistent with what has actually been applied. I will modify the code to set vchanrate to c->speed and vchanformat to c->format at the end, before we unlock the channel.

[christos]

Assign to primary channel parameters.