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authorTakashi Iwai <tiwai@suse.de>2020-03-25 11:33:22 +0100
committerTakashi Iwai <tiwai@suse.de>2020-03-26 10:49:21 +0100
commit2ceb65cd04a9b7d694188b72807f2e1fead16d9c (patch)
treea172a7b315b284374879919d4e733554cf182d0e /Documentation
parenta4aad5636c7298eecfb60fc9d73933336cb0c4d8 (diff)
ALSA: usb-audio: Update the documentation for the new delayed_register option
Just adding a brief explanation to alsa-configuration.rst. Link: https://lore.kernel.org/r/20200325103322.2508-5-tiwai@suse.de Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/sound/alsa-configuration.rst13
1 files changed, 13 insertions, 0 deletions
diff --git a/Documentation/sound/alsa-configuration.rst b/Documentation/sound/alsa-configuration.rst
index 392875a1b94e..72f97d4b01a7 100644
--- a/Documentation/sound/alsa-configuration.rst
+++ b/Documentation/sound/alsa-configuration.rst
@@ -2234,6 +2234,19 @@ use_vmalloc
buffers. If mmap is used on such architectures, turn off this
option, so that the DMA-coherent buffers are allocated and used
instead.
+delayed_register
+ The option is needed for devices that have multiple streams
+ defined in multiple USB interfaces. The driver may invoke
+ registrations multiple times (once per interface) and this may
+ lead to the insufficient device enumeration.
+ This option receives an array of strings, and you can pass
+ ID:INTERFACE like ``0123abcd:4`` for performing the delayed
+ registration to the given device. In this example, when a USB
+ device 0123:abcd is probed, the driver waits the registration
+ until the USB interface 4 gets probed.
+ The driver prints a message like "Found post-registration device
+ assignment: 1234abcd:04" for such a device, so that user can
+ notice the need.
This module supports multiple devices, autoprobe and hotplugging.