linux-kernel - Re: [PATCH v4 3/3] usb: gadget: add f_uac1 variant based on a new u

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Message-ID: <CAB=otbQDruhCUyaUyJFVMF+r7gZ0ecbBnhxiz4uibKBordH1LQ@mail.gmail.com>
Date:   Tue, 30 May 2017 03:07:20 +0300
From:   Ruslan Bilovol <ruslan.bilovol@...il.com>
To:     Julian Scheel <julian@...st.de>
Cc:     Felipe Balbi <balbi@...nel.org>, Daniel Mack <zonque@...il.com>,
        Jassi Brar <jassisinghbrar@...il.com>,
        Clemens Ladisch <clemens@...isch.de>,
        Jonathan Corbet <corbet@....net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Peter Chen <hzpeterchen@...il.com>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        linux-doc@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 3/3] usb: gadget: add f_uac1 variant based on a new
 u_audio api

On Fri, May 26, 2017 at 6:52 PM, Julian Scheel <julian@...st.de> wrote:
> On 18.05.2017 00:37, Ruslan Bilovol wrote:
>>
>> This patch adds a new function 'f_uac1_acard'
>> (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_acard 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_acard 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_acard 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_acard descriptors naming convention
>> uses f_uac2 driver naming convention that
>> makes it more common and meaningful.
>>
>> Comparing to f_uac1, the f_uac1_acard 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_acard functionality, exposed
>> interface to userspace (virtual ALSA card),
>> input parameters are so different comparing
>> to legace f_uac1, 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_acard or f_uac2)
>>
>> Signed-off-by: Ruslan Bilovol <ruslan.bilovol@...il.com>
>> ---
>>   .../ABI/testing/configfs-usb-gadget-uac1_acard     |  14 +
>>   Documentation/usb/gadget-testing.txt               |  45 ++
>>   drivers/usb/gadget/Kconfig                         |  21 +
>>   drivers/usb/gadget/function/Makefile               |   2 +
>>   drivers/usb/gadget/function/f_uac1_acard.c         | 803
>> +++++++++++++++++++++
>>   drivers/usb/gadget/function/u_uac1_acard.h         |  41 ++
>>   drivers/usb/gadget/legacy/Kconfig                  |  15 +-
>>   drivers/usb/gadget/legacy/audio.c                  |  53 ++
>>   8 files changed, 992 insertions(+), 2 deletions(-)
>>   create mode 100644
>> Documentation/ABI/testing/configfs-usb-gadget-uac1_acard
>>   create mode 100644 drivers/usb/gadget/function/f_uac1_acard.c
>>   create mode 100644 drivers/usb/gadget/function/u_uac1_acard.h
>>
>
> Tested on iMX7D using chipidea usb gadget controller. Tested Windows 10 and
> Linux 4.11 as host. Both work fine.
>
> Tested-by: Julian Scheel <julian@...st.de>

Thanks for testing it.

I'll wait for additional reviews/comments next few days and than will
send new patchset with addressed comments.

Also current patchset have minor conflict when applied on top of
Felipe's testing/next branch which is moved to 4.12-rc1. I've
resolved conflict but did only build test so far.
Anyway I uploaded rebased patches to github [1] if anybody
wants to try them.

[1] https://github.com/rbilovol/kernel/commits/usbaudio-v4.12-balbi-testing-next

Best regards,
Ruslan