e89bb42883
This adds interface between userspace and feedback endpoint to report real feedback frequency to the Host. Current implementation adds new userspace interface ALSA mixer control "Capture Pitch 1000000" (similar to aloop driver's "PCM Rate Shift 100000" mixer control) Value in PPM is chosen to have correction value agnostic of the actual HW rate, which the application is not necessarily dealing with, while still retaining a good enough precision to allow smooth clock correction on the playback side, if necessary. Similar to sound/usb/endpoint.c, a slow down is allowed up to 25%. This has no impact on the required bandwidth. Speedup correction has an impact on the bandwidth reserved for the isochronous endpoint. The default allowed speedup is 500ppm. This seems to be more than enough but, if necessary, this is configurable through a module parameter. The reserved bandwidth is rounded up to the next packet size. Usage of this new control is easy to implement in existing userspace tools like alsaloop from alsa-utils. Signed-off-by: Ruslan Bilovol <ruslan.bilovol@gmail.com> Signed-off-by: Jerome Brunet <jbrunet@baylibre.com> Link: https://lore.kernel.org/r/20210603220104.1216001-4-jbrunet@baylibre.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
17 lines
538 B
Plaintext
17 lines
538 B
Plaintext
What: /config/usb-gadget/gadget/functions/uac2.name
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Date: Sep 2014
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KernelVersion: 3.18
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Description:
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The attributes:
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========= ============================
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c_chmask capture channel mask
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c_srate capture sampling rate
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c_ssize capture sample size (bytes)
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c_sync capture synchronization type (async/adaptive)
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fb_max maximum extra bandwidth in async mode
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p_chmask playback channel mask
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p_srate playback sampling rate
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p_ssize playback sample size (bytes)
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========= ============================
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