linux-kernel - Re: [RFC PATCH 0/5] USB Audio Gadget refactoring

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Message-ID: <CAB=otbRg9Xh_qhzw4joR24FtZCyJE=fPpgsj+N3UiTeGY1MhFg@mail.gmail.com>
Date:	Wed, 8 Jun 2016 11:03:03 +0300
From:	Ruslan Bilovol <ruslan.bilovol@...il.com>
To:	Felipe Balbi <balbi@...nel.org>
Cc:	Daniel Mack <zonque@...il.com>,
	Jassi Brar <jassisinghbrar@...il.com>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 0/5] USB Audio Gadget refactoring

Hi guys,

Any feedback on this patch series? Has anybody had a chance to test it?

Regards,
Ruslan

On Tue, May 24, 2016 at 2:50 AM, Ruslan Bilovol
<ruslan.bilovol@...il.com> wrote:
> 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-specfic USB descriptors, some
> boilerplate for configfs, binding and few USB
> config request handling.
>
> Major change to f_uac1 it that it can'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's RFC).
>
> Luckily, 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 is 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
> "never implemented" volume/mute functionality in 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.
>
> Some changes may have lack of good description that may
> be obvious for me but not so clear for others, but I
> hope to fix it in next versions.
>
> Comments, testing are welcome.
>
> Ruslan Bilovol (5):
>   usb: gadget: f_uac2: remove platform driver/device creation
>   usb: gadget: f_uac2: split out audio core
>   usb: gadget: f_uac1: drop volume/mute functionality
>   usb: gadget: f_uac1: switch to u_audio core utilities
>   usb: gadget: f_uac1: add capture support
>
>  drivers/usb/gadget/Kconfig            |  13 +-
>  drivers/usb/gadget/function/Makefile  |   3 +-
>  drivers/usb/gadget/function/f_uac1.c  | 842 +++++++++++++---------------------
>  drivers/usb/gadget/function/f_uac2.c  | 778 ++++---------------------------
>  drivers/usb/gadget/function/u_audio.c | 632 +++++++++++++++++++++++++
>  drivers/usb/gadget/function/u_audio.h |  93 ++++
>  drivers/usb/gadget/function/u_uac1.c  | 314 -------------
>  drivers/usb/gadget/function/u_uac1.h  |  71 +--
>  drivers/usb/gadget/legacy/Kconfig     |   1 +
>  drivers/usb/gadget/legacy/audio.c     |  54 ++-
>  10 files changed, 1208 insertions(+), 1593 deletions(-)
>  create mode 100644 drivers/usb/gadget/function/u_audio.c
>  create mode 100644 drivers/usb/gadget/function/u_audio.h
>  delete mode 100644 drivers/usb/gadget/function/u_uac1.c
>
> --
> 1.9.1
>