From 2ceb65cd04a9b7d694188b72807f2e1fead16d9c Mon Sep 17 00:00:00 2001 From: Takashi Iwai Date: Wed, 25 Mar 2020 11:33:22 +0100 Subject: 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 --- Documentation/sound/alsa-configuration.rst | 13 +++++++++++++ 1 file changed, 13 insertions(+) (limited to 'Documentation/sound') 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. -- cgit v1.2.3