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>
45 lines
872 B
C
45 lines
872 B
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* u_uac2.h
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*
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* Utility definitions for UAC2 function
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*
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* Copyright (c) 2014 Samsung Electronics Co., Ltd.
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* http://www.samsung.com
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*
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* Author: Andrzej Pietrasiewicz <andrzejtp2010@gmail.com>
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*/
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#ifndef U_UAC2_H
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#define U_UAC2_H
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#include <linux/usb/composite.h>
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#define UAC2_DEF_PCHMASK 0x3
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#define UAC2_DEF_PSRATE 48000
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#define UAC2_DEF_PSSIZE 2
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#define UAC2_DEF_CCHMASK 0x3
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#define UAC2_DEF_CSRATE 64000
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#define UAC2_DEF_CSSIZE 2
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#define UAC2_DEF_CSYNC USB_ENDPOINT_SYNC_ASYNC
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#define UAC2_DEF_REQ_NUM 2
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#define UAC2_DEF_FB_MAX 5
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struct f_uac2_opts {
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struct usb_function_instance func_inst;
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int p_chmask;
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int p_srate;
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int p_ssize;
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int c_chmask;
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int c_srate;
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int c_ssize;
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int c_sync;
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int req_number;
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int fb_max;
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bool bound;
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struct mutex lock;
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int refcnt;
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};
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#endif
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