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ALSA: usb-audio: move and add some comments

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Signed-off-by: Daniel Mack <daniel@caiaq.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Daniel Mack
2010-06-16 17:57:30 +02:00
committed by Takashi Iwai
parent 21af7d8c0c
commit 157a57b6fa
3 changed files with 45 additions and 10 deletions
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15
include/linux/usb/audio-v2.h
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@ -18,6 +18,21 @@
/* v1.0 and v2.0 of this standard have many things in common. For the rest
* of the definitions, please refer to audio.h */
/*
* bmControl field decoders
*
* From the USB Audio spec v2.0:
*
* bmaControls() is a (ch+1)-element array of 4-byte bitmaps,
* each containing a set of bit pairs. If a Control is present,
* it must be Host readable. If a certain Control is not
* present then the bit pair must be set to 0b00.
* If a Control is present but read-only, the bit pair must be
* set to 0b01. If a Control is also Host programmable, the bit
* pair must be set to 0b11. The value 0b10 is not allowed.
*
*/
static inline bool uac2_control_is_readable(u32 bmControls, u8 control)
{
return (bmControls >> (control * 2)) & 0x1;