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8b645922b2
This patch adds the support for USB MIDI 2.0 gadget function driver. The driver emulates a USB MIDI 2.0 interface with one or more UMP Endpoints, where each of UMP Endpoint is a pair of MIDI Endpoints for handling MIDI 2.0 UMP packets. When the function driver is bound, the driver creates an ALSA card object with UMP rawmidi devices. This is a kind of loop-back where the incoming and upcoming UMP packets from/to the MIDI 2.0 UMP Endpoints are transferred as-is. In addition, legacy (MIDI 1.0) rawmidi devices are created, so that legacy applications can work in the gadget side, too. When a USB MIDI 2.0 gadget interface appears, the connected host can use it with the snd-usb-audio driver where MIDI 2.0 support is enabled. Both gadget and connected hosts will have the similar UMP Endpoint and Function Block (or Group Terminal Block) information. Slight differences are the direction and UI-hint bits; it's due to the nature of gadget driver, and the input/output direction is swapped in both sides (the input for gadget is the output for host, and vice versa). The driver supports the brand-new UMP v1.1 feature, including the UMP Stream message handling for providing UMP Endpoint and Function Block information as well as dealing with the MIDI protocol switch. The driver responds to UMP Stream messages by itself. OTOH, MIDI-CI message handling isn't implemented in the kernel driver; it should be processed in the user-space through the loopback UMP device. As of this patch, the whole configuration is fixed, providing only one bidirectional UMP Endpoint containing a single FB/GTB with a single UMP Group. The configuration will be dynamically changeable in the following patches. The traditional MIDI 1.0 is still provided in the altset 0 (which is mandatory per spec). But it's only about the configuration, and no actual I/O will be running for the altset 0 as of this patch. The proper support MIDI 1.0 altset will follow in later patches, too. Signed-off-by: Takashi Iwai <tiwai@suse.de> Link: https://lore.kernel.org/r/20230725062206.9674-2-tiwai@suse.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
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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.