usb: gadget: midi2: Add configfs support
This patch adds the support of configfs to MIDI 2.0 function driver for users to allow configuring the UMP Endpoint and Function Blocks more flexibly. The configuration is in a tree form. The top-most contains some card-level configurations. UMP Endpoints are defined in subdirectories (ep.0, ep.1, etc) that contain Endpoint-specific configurations such as ep_name, etc. And, UMP Function Blocks are defined in the subdirectories (block.0, block.1, etc) under EP subdirectory. As default, the driver creates a single UMP Endpoint (ep.0) and a single Function Block (block.0) to work in a minimalistic manner. User can modify those attributes freely to fit with the demands. When multiple Function Blocks are required, user can create another directory as block.1, block.2, and so on (up to block.31). A block.* directory can be deleted dynamically, too. A caveat is that the block number has to be continuous. Similarly, when multiple UMP Endpoints are required, user can create another directory as ep.1, ep.2, up to ep.3. Also, some driver behavior can be controlled in the card top-level configs. e.g. you can pass process_ump=0 to disable the processing of UMP Stream messages. This would be equivalent with the older MIDI 2.0 spec that doesn't support UMP v1.1 features. The configfs interface checks upper- / lower-bound of input values, and more sanity checks are performed at binding. Attributes can't be changed any longer once when the instance is linked to UDC. Signed-off-by: Takashi Iwai <tiwai@suse.de> Link: https://lore.kernel.org/r/20230725062206.9674-3-tiwai@suse.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
parent
8b645922