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03a58514d4
This is a (largish) patch set for adding the support of MIDI 2.0 functionality, mainly targeted for USB devices. MIDI 2.0 is a complete overhaul of the 40-years old MIDI 1.0. Unlike MIDI 1.0 byte stream, MIDI 2.0 uses packets in 32bit words for Universal MIDI Packet (UMP) protocol. It supports both MIDI 1.0 commands for compatibility and the extended MIDI 2.0 commands for higher resolutions and more functions. For supporting the UMP, the patch set extends the existing ALSA rawmidi and sequencer interfaces, and adds the USB MIDI 2.0 support to the standard USB-audio driver. The rawmidi for UMP has a different device name (/dev/snd/umpC*D*) and it reads/writes UMP packet data in 32bit CPU-native endianness. For the old MIDI 1.0 applications, the legacy rawmidi interface is provided, too. As default, USB-audio driver will take the alternate setting for MIDI 2.0 interface, and the compatibility with MIDI 1.0 is provided via the rawmidi common layer. However, user may let the driver falling back to the old MIDI 1.0 interface by a module option, too. A UMP-capable rawmidi device can create the corresponding ALSA sequencer client(s) to support the UMP Endpoint and UMP Group connections. As a nature of ALSA sequencer, arbitrary connections between clients/ports are allowed, and the ALSA sequencer core performs the automatic conversions for the connections between a new UMP sequencer client and a legacy MIDI 1.0 sequencer client. It allows the existing application to use MIDI 2.0 devices without changes. The MIDI-CI, which is another major extension in MIDI 2.0, isn't covered by this patch set. It would be implemented rather in user-space. Roughly speaking, the first half of this patch set is for extending the rawmidi and USB-audio, and the second half is for extending the ALSA sequencer interface. The patch set is based on 6.4-rc2 kernel, but all patches can be cleanly applicable on 6.2 and 6.3 kernels, too (while 6.1 and older kernels would need minor adjustment for uapi header changes). The updates for alsa-lib and alsa-utils will follow shortly later. The author thanks members of MIDI Association OS/API Working Group, especially Andrew Mee, for great helps for the initial design and debugging / testing the drivers. Link: https://lore.kernel.org/r/20230523075358.9672-1-tiwai@suse.de Signed-off-by: Takashi Iwai <tiwai@suse.de> |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.