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ALSA: line6: Add poll callback for hwdep

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At least POD HD500 uses message-based communication, both sides can
send messages. Add poll callback so application can wait for device
messages without using busy loop.

Signed-off-by: Vasily Khoruzhick <anarsoul@gmail.com>
Link: https://lore.kernel.org/r/20200502193120.79115-3-anarsoul@gmail.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Vasily Khoruzhick 2020-05-02 12:31:20 -07:00 committed by Takashi Iwai
parent 5c2d0de544
commit c55f569274
1 changed files with 16 additions and 0 deletions
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16
sound/usb/line6/driver.c
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@ -630,11 +630,27 @@ line6_hwdep_write(struct snd_hwdep *hwdep, const char __user *data, long count,
return rv;
}
static __poll_t
line6_hwdep_poll(struct snd_hwdep *hwdep, struct file *file, poll_table *wait)
{
__poll_t rv;
struct usb_line6 *line6 = hwdep->private_data;
poll_wait(file, &line6->messages.wait_queue, wait);
mutex_lock(&line6->messages.read_lock);
rv = kfifo_len(&line6->messages.fifo) == 0 ? 0 : EPOLLIN | EPOLLRDNORM;
mutex_unlock(&line6->messages.read_lock);
return rv;
}
static const struct snd_hwdep_ops hwdep_ops = {
.open = line6_hwdep_open,
.release = line6_hwdep_release,
.read = line6_hwdep_read,
.write = line6_hwdep_write,
.poll = line6_hwdep_poll,
};
/* Insert into circular buffer */