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>

1 files changed, 52 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/configfs-usb-gadget-midi2 b/Documentation/ABI/testing/configfs-usb-gadget-midi2
new file mode 100644
index 000000000000..a3a036d784c7
--- /dev/null
+++ b/Documentation/ABI/testing/configfs-usb-gadget-midi2
@@ -0,0 +1,52 @@
+What:		/config/usb-gadget/gadget/functions/midi2.name
+Date:		Jul 2023
+KernelVersion:	6.6
+Description:
+		The attributes:
+
+		============	===============================================
+		process_ump	Flag to process UMP Stream messages (0 or 1)
+		static_block	Flag for static blocks (0 or 1)
+		iface_name	MIDI interface name string
+		============	===============================================
+
+What:		/config/usb-gadget/gadget/functions/midi2.name/ep.number
+Date:		Jul 2023
+KernelVersion:	6.6
+Description:
+		This group contains a UMP Endpoint configuration.
+		A new Endpoint starts from 0, and can be up to 3.
+
+		The attributes:
+
+		=============	===============================================
+		protocol_caps	MIDI protocol capabilities (1, 2 or 3 for both)
+		protocol	Default MIDI protocol (1 or 2)
+		ep_name		UMP Endpoint name string
+		product_id	Product ID string
+		manufacturer	Manufacture ID (24 bit)
+		family		Device family ID (16 bit)
+		model		Device model ID (16 bit)
+		sw_revision	Software Revision (32 bit)
+		=============	===============================================
+
+What:		/config/usb-gadget/gadget/functions/midi2.name/ep.number/block.number
+Date:		Jul 2023
+KernelVersion:	6.6
+Description:
+		This group contains a UMP Function Block configuration.
+		A new block starts from 0, and can be up to 31.
+
+		The attributes:
+
+		===============	===============================================
+		name		Function Block name string
+		direction	1: input, 2: output, 3: bidirectional
+		first_group	The first UMP Group number (0-15)
+		num_groups	The number of groups in this FB (1-16)
+		ui_hint		0: unknown, 1: receiver, 2: sender, 3: both
+		midi_ci_verison	Supported MIDI-CI version number (8 bit)
+		is_midi1	Legacy MIDI 1.0 device (0, 1 or 2)
+		sysex8_streams	Max number of SysEx8 streams (8 bit)
+		active		Active FB flag (0 or 1)
+		===============	===============================================