Date:   Sun, 25 Jun 2017 22:09:42 +0530
From:   Jassi Brar <jassisinghbrar@...il.com>
To:     Ruslan Bilovol <ruslan.bilovol@...il.com>
Cc:     Felipe Balbi <balbi@...nel.org>, Daniel Mack <zonque@...il.com>,
        Clemens Ladisch <clemens@...isch.de>,
        Jonathan Corbet <corbet@....net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Peter Chen <hzpeterchen@...il.com>,
        Julian Scheel <julian@...st.de>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        linux-doc@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 0/4] USB Audio Gadget refactoring

On Sun, Jun 18, 2017 at 6:53 PM, Ruslan Bilovol
<ruslan.bilovol@...il.com> wrote:
> Hi Felipe,
>
> This is v5 of audio gadget refactoring.
> Note, that legacy f_uac1 function is broken since v4.10
> by commit 7e4da3fcf7c9 ("usb: gadget: composite: Test
> get_alt() presence instead of set_alt()"). The fact that
> at v4.12-rc5 time nobody cares about may be a good sign
> that number of users is small if any. Thus making it
> legacy makes sence.
>
> This series depends on legacy f_uac1 fix I posted before:
> http://www.spinics.net/lists/linux-usb/msg158373.html
> Without this fix it's not possible to check that refactoring
> didn't break legacy f_uac1 functionality
>
> ========================================
>
> I came to this patch series when wanted to do two things:
>  - use UAC1 as virtual ALSA sound card on gadget side,
>    just like UAC2 is used so it's possible to do rate
>    resampling
>  - have both playback/capture support in UAC1
>
> Since I wanted to have same behavior for both UAC1/UAC2,
> obviously I've got an utility part (u_audio.c) for
> virtual ALSA sound card handling like we have
> for ethernet(u_ether) or serial(u_serial) functions.
> Function-specific parts (f_uac1/f_uac2) became almost
> as storage for class-specific USB descriptors, some
> boilerplate for configfs, binding and few USB
> config request handling.
>
> Originally in RFC [1] I've posted before, there was
> major change to f_uac1 after that it couldn't do
> direct play to existing ALSA sound card anymore,
> representing audio on gadget side as virtual
> ALSA sound card where audio streams are simply
> sinked to and sourced from it, so it may break
> current usecase for some people (and that's why
> it was RFC).
>
> During RFC discussion, it was agreed to not touch
> existing f_uac1 implementation and create new one
> instead. At v4 patchet discussion another approach
> was agreed - current f_uac1.c gets renamed to
> f_uac1_legacy.c and introduced a *new* f_uac1.c
> instead that is done in current patchset (v5)
>
> Now, it's possible to use existing user-space
> applications for audio routing between Audio Gadget
> and real sound card. I personally use alsaloop tool
> from alsautils and have ability to create PCM
> loopback between two different ALSA cards using
> rate resampling, which was not possible with previous
> "direct play to ALSA card" approach in f_uac1.
>
> While here, also dropped redundant platform
> driver/device creation in f_uac2 driver (as well as
> didn't add "never implemented" volume/mute functionality
> in f_uac1_legacy to f_uac1) that made this work even
> easier to do.
>
> This series is tested with both legacy g_audio.ko and
> modern configfs approaches under Ubuntu 14.04 (UAC1 and
> UAC2) and under Windows7 x64 (UAC1 only) having
> perfect results in all cases.
>
> Comments, testing are welcome.
>
> v5 changes:
>  - after discussion with Felipe, switched to another
>    approach with making current f_uac1 legacy and
>    introducing a new f_uac1.c instead
>  - addressed Jassi's copyright comments
>
> v4 changes:
>  - renamed f_uac1_newapi to f_uac1_acard that is
>    more meaningful
>  - rebased on top of balbi/next
>
> v3 changes:
>  - renamed u_audio exported symbols so they don't
>    conflict with old f_uac1 if both are built-in.
>
> v2 changes:
>  - do not touch f_uac1, instead created f_uac1_newapi
>  - added documentation for f_uac1_newapi
>  - rebased on top of v4.8-rc1
>
> [1] https://lkml.org/lkml/2016/5/23/649
>
> Ruslan Bilovol (4):
>   usb: gadget: f_uac2: remove platform driver/device creation
>   usb: gadget: f_uac2: split out audio core
>   usb: gadget: function: make current f_uac1 implementation legacy
>   usb: gadget: add f_uac1 variant based on a new u_audio api
>
>  Documentation/ABI/testing/configfs-usb-gadget-uac1 |   18 +-
>  .../ABI/testing/configfs-usb-gadget-uac1_legacy    |   12 +
>  Documentation/usb/gadget-testing.txt               |   53 +-
>  drivers/usb/gadget/Kconfig                         |   29 +-
>  drivers/usb/gadget/function/Makefile               |    5 +-
>  drivers/usb/gadget/function/f_uac1.c               |  906 +++++++----------
>  drivers/usb/gadget/function/f_uac1_legacy.c        | 1021 ++++++++++++++++++++
>  drivers/usb/gadget/function/f_uac2.c               |  795 ++-------------
>  drivers/usb/gadget/function/u_audio.c              |  662 +++++++++++++
>  drivers/usb/gadget/function/u_audio.h              |   95 ++
>  drivers/usb/gadget/function/u_uac1.h               |   87 +-
>  .../gadget/function/{u_uac1.c => u_uac1_legacy.c}  |    7 +-
>  drivers/usb/gadget/function/u_uac1_legacy.h        |   82 ++
>  drivers/usb/gadget/legacy/Kconfig                  |   15 +-
>  drivers/usb/gadget/legacy/audio.c                  |   55 +-
>  15 files changed, 2494 insertions(+), 1348 deletions(-)
>  create mode 100644 Documentation/ABI/testing/configfs-usb-gadget-uac1_legacy
>  create mode 100644 drivers/usb/gadget/function/f_uac1_legacy.c
>  create mode 100644 drivers/usb/gadget/function/u_audio.c
>  create mode 100644 drivers/usb/gadget/function/u_audio.h
>  rename drivers/usb/gadget/function/{u_uac1.c => u_uac1_legacy.c} (98%)
>  create mode 100644 drivers/usb/gadget/function/u_uac1_legacy.h
>
Acked-by: Jassi Brar <jassisinghbrar@...il.com>

Thanks.

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