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976b6c064a
This patch changes the way URBs are allocated and their sizes are determined for PCM playback in the snd-usb-audio driver. Currently the driver allocates too few URBs for endpoints that don't use implicit sync, making underruns more likely to occur. This may be a holdover from before I/O delays could be measured accurately; in any case, it is no longer necessary. The patch allocates as many URBs as possible, subject to four limitations: The total number of URBs for the endpoint is not allowed to exceed MAX_URBS (which the patch increases from 8 to 12). The total number of packets per URB is not allowed to exceed MAX_PACKS (or MAX_PACKS_HS for high-speed devices), which is decreased from 20 to 6. The total duration of queued data is not allowed to exceed MAX_QUEUE, which is decreased from 24 ms to 18 ms. The total number of ALSA frames in the output queue is not allowed to exceed the ALSA buffer size. The last requirement is the hardest to implement. Currently the number of URBs needed to fill a buffer cannot be determined in advance, because a buffer contains a fixed number of frames whereas the number of frames in an URB varies to match shifts in the device's clock rate. To solve this problem, the patch changes the logic for deciding how many packets an URB should contain. Rather than using as many as possible without exceeding an ALSA period boundary, now the driver uses only as many packets as needed to transfer a predetermined number of frames. As a result, unless the device's clock has an exceedingly variable rate, the number of URBs making up each period (and hence each buffer) will remain constant. The overall effect of the patch is that playback works better in low-latency settings. The user can still specify values for frames/period and periods/buffer that exceed the capabilities of the hardware, of course. But for values that are within those capabilities, the performance will be improved. For example, testing shows that a high-speed device can handle 32 frames/period and 3 periods/buffer at 48 KHz, whereas the current driver starts to get glitchy at 64 frames/period and 2 periods/buffer. A side effect of these changes is that the "nrpacks" module parameter is no longer used. The patch removes it. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> CC: Clemens Ladisch <clemens@ladisch.de> Tested-by: Daniel Mack <zonque@gmail.com> Tested-by: Eldad Zack <eldad@fogrefinery.com> Signed-off-by: Takashi Iwai <tiwai@suse.de>
109 lines
2.9 KiB
C
109 lines
2.9 KiB
C
#ifndef __USBAUDIO_H
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#define __USBAUDIO_H
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/*
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* (Tentative) USB Audio Driver for ALSA
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*
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* Copyright (c) 2002 by Takashi Iwai <tiwai@suse.de>
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*
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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/* handling of USB vendor/product ID pairs as 32-bit numbers */
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#define USB_ID(vendor, product) (((vendor) << 16) | (product))
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#define USB_ID_VENDOR(id) ((id) >> 16)
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#define USB_ID_PRODUCT(id) ((u16)(id))
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/*
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*
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*/
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struct snd_usb_audio {
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int index;
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struct usb_device *dev;
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struct snd_card *card;
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struct usb_interface *pm_intf;
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u32 usb_id;
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struct mutex mutex;
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struct rw_semaphore shutdown_rwsem;
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unsigned int shutdown:1;
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unsigned int probing:1;
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unsigned int autosuspended:1;
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unsigned int txfr_quirk:1; /* Subframe boundaries on transfers */
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int num_interfaces;
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int num_suspended_intf;
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struct list_head pcm_list; /* list of pcm streams */
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struct list_head ep_list; /* list of audio-related endpoints */
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int pcm_devs;
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struct list_head midi_list; /* list of midi interfaces */
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struct list_head mixer_list; /* list of mixer interfaces */
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int setup; /* from the 'device_setup' module param */
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bool autoclock; /* from the 'autoclock' module param */
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struct usb_host_interface *ctrl_intf; /* the audio control interface */
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};
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/*
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* Information about devices with broken descriptors
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*/
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/* special values for .ifnum */
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#define QUIRK_NO_INTERFACE -2
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#define QUIRK_ANY_INTERFACE -1
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enum quirk_type {
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QUIRK_IGNORE_INTERFACE,
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QUIRK_COMPOSITE,
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QUIRK_AUTODETECT,
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QUIRK_MIDI_STANDARD_INTERFACE,
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QUIRK_MIDI_FIXED_ENDPOINT,
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QUIRK_MIDI_YAMAHA,
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QUIRK_MIDI_ROLAND,
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QUIRK_MIDI_MIDIMAN,
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QUIRK_MIDI_NOVATION,
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QUIRK_MIDI_RAW_BYTES,
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QUIRK_MIDI_EMAGIC,
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QUIRK_MIDI_CME,
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QUIRK_MIDI_AKAI,
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QUIRK_MIDI_US122L,
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QUIRK_MIDI_FTDI,
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QUIRK_AUDIO_STANDARD_INTERFACE,
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QUIRK_AUDIO_FIXED_ENDPOINT,
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QUIRK_AUDIO_EDIROL_UAXX,
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QUIRK_AUDIO_ALIGN_TRANSFER,
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QUIRK_AUDIO_STANDARD_MIXER,
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QUIRK_TYPE_COUNT
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};
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struct snd_usb_audio_quirk {
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const char *vendor_name;
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const char *product_name;
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int16_t ifnum;
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uint16_t type;
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const void *data;
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};
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#define combine_word(s) ((*(s)) | ((unsigned int)(s)[1] << 8))
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#define combine_triple(s) (combine_word(s) | ((unsigned int)(s)[2] << 16))
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#define combine_quad(s) (combine_triple(s) | ((unsigned int)(s)[3] << 24))
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#endif /* __USBAUDIO_H */
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