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The prepare_data_urb and retire_data_urb fields of the endpoint object are set dynamically at PCM trigger start/stop. Those are evaluated in the endpoint handler, but there can be a race, especially if two different PCM substreams are handling the same endpoint for the implicit feedback case. Also, the data_subs field of the endpoint is set and accessed dynamically, too, which has the same risk. As a slight improvement for the concurrency, this patch introduces the function to set the callbacks and the data in a shot with the memory barrier. In the reader side, it's also fetched with the memory barrier. There is still a room of race if prepare and retire callbacks are set during executing the URB completion. But such an inconsistency may happen only for the implicit fb source, i.e. it's only about the capture stream. And luckily, the capture stream never sets the prepare callback, hence the problem doesn't happen practically. Tested-by: Keith Milner <kamilner@superlative.org> Tested-by: Dylan Robinson <dylan_robinson@motu.com> Link: https://lore.kernel.org/r/20201123085347.19667-23-tiwai@suse.de Signed-off-by: Takashi Iwai <tiwai@suse.de>
50 lines
1.9 KiB
C
50 lines
1.9 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef __USBAUDIO_ENDPOINT_H
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#define __USBAUDIO_ENDPOINT_H
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#define SND_USB_ENDPOINT_TYPE_DATA 0
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#define SND_USB_ENDPOINT_TYPE_SYNC 1
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struct snd_usb_endpoint *snd_usb_get_endpoint(struct snd_usb_audio *chip,
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int ep_num);
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int snd_usb_add_endpoint(struct snd_usb_audio *chip, int ep_num, int type);
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int snd_usb_endpoint_set_params(struct snd_usb_endpoint *ep,
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snd_pcm_format_t pcm_format,
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unsigned int channels,
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unsigned int period_bytes,
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unsigned int period_frames,
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unsigned int buffer_periods,
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unsigned int rate,
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struct audioformat *fmt,
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struct snd_usb_endpoint *sync_ep);
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void snd_usb_endpoint_set_callback(struct snd_usb_endpoint *ep,
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void (*prepare)(struct snd_usb_substream *subs,
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struct urb *urb),
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void (*retire)(struct snd_usb_substream *subs,
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struct urb *urb),
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struct snd_usb_substream *data_subs);
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int snd_usb_endpoint_start(struct snd_usb_endpoint *ep);
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void snd_usb_endpoint_stop(struct snd_usb_endpoint *ep);
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void snd_usb_endpoint_sync_pending_stop(struct snd_usb_endpoint *ep);
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int snd_usb_endpoint_activate(struct snd_usb_endpoint *ep);
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void snd_usb_endpoint_deactivate(struct snd_usb_endpoint *ep);
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void snd_usb_endpoint_release(struct snd_usb_endpoint *ep);
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void snd_usb_endpoint_free(struct snd_usb_endpoint *ep);
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int snd_usb_endpoint_implicit_feedback_sink(struct snd_usb_endpoint *ep);
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int snd_usb_endpoint_slave_next_packet_size(struct snd_usb_endpoint *ep);
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int snd_usb_endpoint_next_packet_size(struct snd_usb_endpoint *ep);
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void snd_usb_endpoint_set_syncinterval(struct snd_usb_audio *chip,
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struct snd_usb_endpoint *ep,
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struct usb_host_interface *alts);
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void snd_usb_handle_sync_urb(struct snd_usb_endpoint *ep,
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struct snd_usb_endpoint *sender,
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const struct urb *urb);
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#endif /* __USBAUDIO_ENDPOINT_H */
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