ALSA: usb-audio: Add keep_iface flag

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Introduce a new flag to struct snd_usb_audio for allowing the device
to skip usb_set_interface() calls at changing or closing the stream.
As of this patch, the flag is nowhere set, so it's just a place
holder.  The dynamic switching will be added in the following patch.

A background information for this change:

Dell WD15 dock with Realtek chip gives a very long pause at each time
the driver changes the altset, which eventually happens at every PCM
stream open/close and parameter change.  As the long pause happens in
each usb_set_interface() call, there is nothing we can do as long as
it's called.  The workaround is to reduce calling it as much as
possible, and this flag indicates that behavior.

Signed-off-by: Takashi Iwai <tiwai@suse.de>

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This commit is contained in:

Takashi Iwai 2018-05-02 10:04:27 +02:00

parent b099b9693d

commit 8a463225b1

2 changed files with 13 additions and 7 deletions

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17

sound/usb/pcm.c

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3

sound/usb/usbaudio.h

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