RE: [PATCH 0/6] Ancillary bus implementation and SOF multi-client support

["Ertman, David M" <david.m.ertman@intel.com>]

-DaveE

> -----Original Message-----
> From: Alsa-devel <alsa-devel-bounces@alsa-project.org> On Behalf Of Dave
> Ertman
> Sent: Wednesday, September 30, 2020 3:51 PM
> To: alsa-devel@alsa-project.org
> Cc: tiwai@suse.de; gregkh@linuxfoundation.org; Sridharan, Ranjani
> <ranjani.sridharan@intel.com>; pierre-louis.bossart@linux.intel.com;
> broonie@kernel.org; parav@nvidia.com; jgg@nvidia.com
> Subject: [PATCH 0/6] Ancillary bus implementation and SOF multi-client
> support
> 
> Brief history of Ancillary Bus
> ==============================
> The ancillary bus code was originally submitted upstream as virtual
> bus, and was submitted through the netdev tree.  This process generated
> up to v4.  This discussion can be found here:
>  https://lore.kernel.org/netdev/0200520070227.3392100-2-
> jeffrey.t.kirsher@intel.com/T/#u

Sorry, this is a borked link.  Will fix with actual link:

https://lore.kernel.org/netdev/20191111192219.30259-1-jeffrey.t.kirsher@intel.com/#t

this was the original submission of virtual bus in Nov 2019.

> 
> At this point, GregKH requested that we take the review and revision
> process to an internal mailing list and garner the buy-in of a respected
> kernel contributor.
> 
> The ancillary bus (then known as virtual bus) was originally submitted
> along with implementation code for the ice driver and irdma drive,
> causing the complication of also having dependencies in the rdma tree.
> This new submission is utilizing an ancillary bus consumer in only the
> sound driver tree to create the initial implementation and a single
> user.
> 
> Since implementation work has started on this patch set, there have been
> multiple inquiries about the time frame of its completion.  It appears
> that there will be numerous consumers of this functionality.
> 
> The process of internal review and implementation using the sound
> drivers generated 19 internal versions.  The changes, including the name
> change from virtual bus to ancillary bus, from these versions can be
> summarized as the following:
> 
> - Fixed compilation and checkpatch errors
> - Improved documentation to address the motivation for virtual bus.
> - Renamed virtual bus to ancillary bus
> - increased maximum device name size
> - Correct order in Kconfig and Makefile
> - removed the mid-layer adev->release layer for device unregister
> - pushed adev->id management to parent driver
> - all error paths out of ancillary_device_register return error code
> - all error paths out of ancillary_device_register use put_device
> - added adev->name element
> - modname in register cannot be NULL
> - added KBUILD_MODNAME as prefix for match_name
> - push adev->id responsibility to registering driver
> - uevent now parses adev->dev name
> - match_id function now parses adev->dev name
> - changed drivers probe function to also take an ancillary_device_id param
> - split ancillary_device_register into device_initialize and device_add
> - adjusted what is done in device_initialize and device_add
> - change adev to ancildev and adrv to ancildrv
> - change adev to ancildev in documentation
> 
> This submission is the first time that this patch set will be sent to
> the alsa-devel mailing list, so it is currently being submitted as
> version 1.
> 
> ==========================
> 
> Introduces the ancillary bus implementation along with the example usage
> in the Sound Open Firmware(SOF) audio driver.
> 
> In some subsystems, the functionality of the core device
> (PCI/ACPI/other) may be too complex for a single device to be managed as
> a monolithic block or a part of the functionality might need to be
> exposed to a different subsystem.  Splitting the functionality into
> smaller orthogonal devices makes it easier to manage data, power
> management and domain-specific communication with the hardware.  Also,
> common ancillary_device functionality across primary devices can be
> handled by a common ancillary_device. A key requirement for such a split
> is that there is no dependency on a physical bus, device, register
> accesses or regmap support. These individual devices split from the core
> cannot live on the platform bus as they are not physical devices that
> are controlled by DT/ACPI. The same argument applies for not using MFD
> in this scenario as it relies on individual function devices being
> physical devices that are DT enumerated.
> 
> An example for this kind of requirement is the audio subsystem where a
> single IP handles multiple entities such as HDMI, Soundwire, local
> devices such as mics/speakers etc. The split for the core's
> functionality can be arbitrary or be defined by the DSP firmware
> topology and include hooks for test/debug. This allows for the audio
> core device to be minimal and tightly coupled with handling the
> hardware-specific logic and communication.
> 
> The ancillary bus is intended to be minimal, generic and avoid
> domain-specific assumptions. Each ancillary bus device represents a part
> of its parent functionality. The generic behavior can be extended and
> specialized as needed by encapsulating an ancillary bus device within
> other domain-specific structures and the use of .ops callbacks.
> 
> The SOF driver adopts the ancillary bus for implementing the
> multi-client support. A client in the context of the SOF driver
> represents a part of the core device's functionality. It is not a
> physical device but rather an ancillary device that needs to communicate
> with the DSP via IPCs. With multi-client support,the sound card can be
> separated into multiple orthogonal ancillary devices for local devices
> (mic/speakers etc), HDMI, sensing, probes, debug etc.  In this series,
> we demonstrate the usage of the ancillary bus with the help of the IPC
> test client which is used for testing the serialization of IPCs when
> multiple clients talk to the DSP at the same time.
> 
> Dave Ertman (1):
>   Add ancillary bus support
> 
> Fred Oh (1):
>   ASoC: SOF: debug: Remove IPC flood test support in SOF core
> 
> Ranjani Sridharan (4):
>   ASoC: SOF: Introduce descriptors for SOF client
>   ASoC: SOF: Create client driver for IPC test
>   ASoC: SOF: ops: Add ops for client registration
>   ASoC: SOF: Intel: Define ops for client registration
> 
>  Documentation/driver-api/ancillary_bus.rst | 230 +++++++++++++++
>  Documentation/driver-api/index.rst         |   1 +
>  drivers/bus/Kconfig                        |   3 +
>  drivers/bus/Makefile                       |   3 +
>  drivers/bus/ancillary.c                    | 191 +++++++++++++
>  include/linux/ancillary_bus.h              |  58 ++++
>  include/linux/mod_devicetable.h            |   8 +
>  scripts/mod/devicetable-offsets.c          |   3 +
>  scripts/mod/file2alias.c                   |   8 +
>  sound/soc/sof/Kconfig                      |  29 +-
>  sound/soc/sof/Makefile                     |   7 +
>  sound/soc/sof/core.c                       |  12 +
>  sound/soc/sof/debug.c                      | 230 ---------------
>  sound/soc/sof/intel/Kconfig                |   9 +
>  sound/soc/sof/intel/Makefile               |   3 +
>  sound/soc/sof/intel/apl.c                  |  18 ++
>  sound/soc/sof/intel/bdw.c                  |  18 ++
>  sound/soc/sof/intel/byt.c                  |  22 ++
>  sound/soc/sof/intel/cnl.c                  |  18 ++
>  sound/soc/sof/intel/intel-client.c         |  49 ++++
>  sound/soc/sof/intel/intel-client.h         |  26 ++
>  sound/soc/sof/ops.h                        |  14 +
>  sound/soc/sof/sof-client.c                 | 117 ++++++++
>  sound/soc/sof/sof-client.h                 |  65 +++++
>  sound/soc/sof/sof-ipc-test-client.c        | 314 +++++++++++++++++++++
>  sound/soc/sof/sof-priv.h                   |  16 +-
>  26 files changed, 1233 insertions(+), 239 deletions(-)
>  create mode 100644 Documentation/driver-api/ancillary_bus.rst
>  create mode 100644 drivers/bus/ancillary.c
>  create mode 100644 include/linux/ancillary_bus.h
>  create mode 100644 sound/soc/sof/intel/intel-client.c
>  create mode 100644 sound/soc/sof/intel/intel-client.h
>  create mode 100644 sound/soc/sof/sof-client.c
>  create mode 100644 sound/soc/sof/sof-client.h
>  create mode 100644 sound/soc/sof/sof-ipc-test-client.c
> 
> --
> 2.26.2