There have been a few enhancements for the new UMP 1.1 features.
Update the documentation accordingly.
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
---
Documentation/sound/designs/midi-2.0.rst | 39 ++++++++++++++++++++----
1 file changed, 33 insertions(+), 6 deletions(-)
diff --git a/Documentation/sound/designs/midi-2.0.rst b/Documentation/sound/designs/midi-2.0.rst
index d55b0a4c6acb..27d0d3dea1b0 100644
--- a/Documentation/sound/designs/midi-2.0.rst
+++ b/Documentation/sound/designs/midi-2.0.rst
@@ -68,6 +68,15 @@ default instead of the MIDI 1.0 interface (at altset 0). You can
switch back to the binding with the old MIDI 1.0 interface by passing
`midi2_enable=0` option to snd-usb-audio driver module, too.
+The USB audio driver tries to query the UMP Endpoint and UMP Function
+Block information that are provided since UMP v1.1, and builds up the
+topology based on those information. When the device is older and
+doesn't respond to the new UMP inquiries, the driver falls back and
+builds the topology based on Group Terminal Block (GTB) information
+from the USB descriptor. Some device might be screwed up by the
+unexpected UMP command; in such a case, pass `midi2_probe=0` option to
+snd-usb-audio driver for skipping the UMP v1.1 inquiries.
+
When the MIDI 2.0 device is probed, the kernel creates a rawmidi
device for each UMP Endpoint of the device. Its device name is
`/dev/snd/umpC*D*` and different from the standard rawmidi device name
@@ -101,11 +110,15 @@ opening `/dev/snd/midiC*D*` will end up with opening the first
substream.
Each UMP Endpoint can provide the additional information, constructed
-from USB MIDI 2.0 descriptors. And a UMP Endpoint may contain one or
-more UMP Blocks, where UMP Block is an abstraction introduced in the
-ALSA UMP implementations to represent the associations among UMP
-Groups. UMP Block corresponds to Group Terminal Block (GTB) in USB
-MIDI 2.0 specifications but provide a few more generic information.
+from the information inquired via UMP 1.1 Stream messages or USB MIDI
+2.0 descriptors. And a UMP Endpoint may contain one or more UMP
+Blocks, where UMP Block is an abstraction introduced in the ALSA UMP
+implementations to represent the associations among UMP Groups. UMP
+Block corresponds to Function Block in UMP 1.1 specification. When
+UMP 1.1 Function Block information isn't available, it's filled
+partially from Group Terminal Block (GTB) as defined in USB MIDI 2.0
+specifications.
+
The information of UMP Endpoints and UMP Blocks are found in the proc
file `/proc/asound/card*/midi*`. For example::
@@ -207,6 +220,8 @@ The "MIDI 2.0" port is for a UMP Endpoint, and its difference from
other UMP Group ports is that UMP Endpoint port sends the events from
the all ports on the device ("catch-all"), while each UMP Group port
sends only the events from the given UMP Group.
+Also, UMP groupless messages (such as the UMP message type 0x0f) are
+sent only to the UMP Endpoint port.
Note that, although each UMP sequencer client usually creates 16
ports, those ports that don't belong to any UMP Blocks (or belonging
@@ -273,6 +288,11 @@ Rawmidi API Extensions
The direction is either `SNDRV_UMP_DIR_INPUT`,
`SNDRV_UMP_DIR_OUTPUT` or `SNDRV_UMP_DIR_BIDIRECTION`.
+* For the device supports UMP v1.1, the UMP MIDI protocol can be
+ switched via "Stream Configuration Request" message (UMP type 0x0f,
+ status 0x05). When UMP core receives such a message, it updates the
+ UMP EP info and the corresponding sequencer clients as well.
+
Control API Extensions
======================
@@ -337,7 +357,7 @@ Sequencer API Extensions
`group_filter` bitmap. The filter consists of bitmap from 1-based
Group numbers. For example, when the bit 1 is set, messages from
Group 1 (i.e. the very first group) are filtered and not delivered.
- The bit 0 is reserved for future use.
+ The bit 0 is used for filtering UMP groupless messages.
* Two new ioctls are added for UMP-capable clients:
`SNDRV_SEQ_IOCTL_GET_CLIENT_UMP_INFO` and
@@ -349,3 +369,10 @@ Sequencer API Extensions
For an Endpoint data, pass 0 to the `type` field, while for a Block
data, pass the block number + 1 to the `type` field.
Setting the data for a kernel client shall result in an error.
+
+* With UMP 1.1, Function Block information may be changed
+ dynamically. When the update of Function Block is received from the
+ device, ALSA sequencer core changes the corresponding sequencer port
+ name and attributes accordingly, and notifies the changes via the
+ announcement to the ALSA sequencer system port, similarly like the
+ normal port change notification.
--
2.35.3
