Commit 0591bc23 authored by Ruslan Bilovol's avatar Ruslan Bilovol Committed by Felipe Balbi
Browse files

usb: gadget: add f_uac1 variant based on a new u_audio api 



This patch adds a new function 'f_uac1'
(f_uac1 with virtual "ALSA card") that
uses recently created u_audio API. Comparing
to legacy f_uac1 function implementation it
doesn't require any real Audio codec to be
present on the device. In f_uac1 audio
streams are simply sinked to and sourced
from a virtual ALSA sound card created
using u_audio API.

Legacy f_uac1 approach is to write audio
samples directly to existing ALSA sound
card

f_uac1 approach is more generic/flexible
one - create an ALSA sound card that
represents USB Audio function and allows to
be used by userspace application that
may choose to do whatever it wants with the
data received from the USB Host and choose
to provide whatever it wants as audio data
to the USB Host.

f_uac1 also has capture support (gadget->host)
thanks to easy implementation via u_audio.
By default, capture interface has 48000kHz/2ch
configuration, same as playback channel has.

f_uac1 descriptors naming convention
uses f_uac2 driver naming convention that
makes it more common and meaningful.

Comparing to f_uac1_legacy, the f_uac1 doesn't
have volume/mute functionality. This is because
the f_uac1 volume/mute feature unit was dummy
implementation since that driver creation (2009)
and never had any real volume control or mute
functionality, so there is no any difference
here.

Since f_uac1 functionality, exposed
interface to userspace (virtual ALSA card),
input parameters are so different comparing
to f_uac1_legacy, that there is no any
reason to keep them in the same file/module,
and separate function was created.

g_audio can be built using one of existing
UAC functions (f_uac1, f_uac1_legacy or f_uac2)

Signed-off-by: default avatarRuslan Bilovol <ruslan.bilovol@gmail.com>
Signed-off-by: default avatarFelipe Balbi <felipe.balbi@linux.intel.com>
parent d355339e

Documentation/ABI/testing/configfs-usb-gadget-uac1

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What:		/config/usb-gadget/gadget/functions/uac1.name

Date:		June 2017

KernelVersion:	4.14

Description:

		The attributes:



		c_chmask - capture channel mask

		c_srate - capture sampling rate

		c_ssize - capture sample size (bytes)

		p_chmask - playback channel mask

		p_srate - playback sampling rate

		p_ssize - playback sample size (bytes)

		req_number - the number of pre-allocated request

			for both capture and playback

Documentation/usb/gadget-testing.txt

+44 −0
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@@ -20,6 +20,7 @@ provided by gadgets. 
17. UAC2 function

18. UVC function

19. PRINTER function

20. UAC1 function (new API)





1. ACM function
@@ -773,3 +774,46 @@ host: 


More advanced testing can be done with the prn_example

described in Documentation/usb/gadget-printer.txt.





20. UAC1 function (virtual ALSA card, using u_audio API)

=================



The function is provided by usb_f_uac1.ko module.

It will create a virtual ALSA card and the audio streams are simply

sinked to and sourced from it.



Function-specific configfs interface

------------------------------------



The function name to use when creating the function directory is "uac1".

The uac1 function provides these attributes in its function directory:



	c_chmask - capture channel mask

	c_srate - capture sampling rate

	c_ssize - capture sample size (bytes)

	p_chmask - playback channel mask

	p_srate - playback sampling rate

	p_ssize - playback sample size (bytes)

	req_number - the number of pre-allocated request for both capture

		     and playback



The attributes have sane default values.



Testing the UAC1 function

-------------------------



device: run the gadget

host: aplay -l # should list our USB Audio Gadget



This function does not require real hardware support, it just

sends a stream of audio data to/from the host. In order to

actually hear something at the device side, a command similar

to this must be used at the device side:



$ arecord -f dat -t wav -D hw:2,0 | aplay -D hw:0,0 &



e.g.:



$ arecord -f dat -t wav -D hw:CARD=UAC1Gadget,DEV=0 | \

aplay -D default:CARD=OdroidU3

drivers/usb/gadget/Kconfig

+23 −2
Original line number Diff line number Diff line
@@ -191,6 +191,9 @@ config USB_F_MASS_STORAGE 
config USB_F_FS

	tristate



config USB_F_UAC1

	tristate



config USB_F_UAC1_LEGACY

	tristate
@@ -365,6 +368,24 @@ config USB_CONFIGFS_F_FS 
	  implemented in kernel space (for instance Ethernet, serial or

	  mass storage) and other are implemented in user space.



config USB_CONFIGFS_F_UAC1

	bool "Audio Class 1.0"

	depends on USB_CONFIGFS

	depends on SND

	select USB_LIBCOMPOSITE

	select SND_PCM

	select USB_U_AUDIO

	select USB_F_UAC1

	help

	  This Audio function implements 1 AudioControl interface,

	  1 AudioStreaming Interface each for USB-OUT and USB-IN.

	  This driver doesn't expect any real Audio codec to be present

	  on the device - the audio streams are simply sinked to and

	  sourced from a virtual ALSA sound card created. The user-space

	  application may choose to do whatever it wants with the data

	  received from the USB Host and choose to provide whatever it

	  wants as audio data to the USB Host.



config USB_CONFIGFS_F_UAC1_LEGACY

	bool "Audio Class 1.0 (legacy implementation)"

	depends on USB_CONFIGFS
@@ -375,8 +396,8 @@ config USB_CONFIGFS_F_UAC1_LEGACY 
	help

	  This Audio function implements 1 AudioControl interface,

	  1 AudioStreaming Interface each for USB-OUT and USB-IN.

	  This driver requires a real Audio codec to be present

	  on the device.

	  This is a legacy driver and requires a real Audio codec

	  to be present on the device.



config USB_CONFIGFS_F_UAC2

	bool "Audio Class 2.0"

drivers/usb/gadget/function/Makefile

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@@ -33,6 +33,8 @@ obj-$(CONFIG_USB_F_MASS_STORAGE)+= usb_f_mass_storage.o 
usb_f_fs-y			:= f_fs.o

obj-$(CONFIG_USB_F_FS)		+= usb_f_fs.o

obj-$(CONFIG_USB_U_AUDIO)	+= u_audio.o

usb_f_uac1-y			:= f_uac1.o

obj-$(CONFIG_USB_F_UAC1)	+= usb_f_uac1.o

usb_f_uac1_legacy-y		:= f_uac1_legacy.o u_uac1_legacy.o

obj-$(CONFIG_USB_F_UAC1_LEGACY)	+= usb_f_uac1_legacy.o

usb_f_uac2-y			:= f_uac2.o

drivers/usb/gadget/function/f_uac1.c

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