[PATCH 0/2] ALSA: line6: hwdep: add support for poll and non-blocking read
This series adds support for polling and non-blocking read for hwdep interface. This allows apps to listen to HW events without using busy loop.
Example of app that uses hwdep interface for POD HD500 can be found here: https://github.com/anarsoul/line6_hwdep_test
Vasily Khoruzhick (2): ALSA: line6: hwdep: add support for O_NONBLOCK opening mode ALSA: line6: Add poll callback for hwdep
sound/usb/line6/driver.c | 20 ++++++++++++++++++++ sound/usb/line6/driver.h | 1 + 2 files changed, 21 insertions(+)
Currently line6 hwdep interface ignores O_NONBLOCK flag when opening device and it renders it somewhat useless when using poll.
Check for O_NONBLOCK flag when opening device and don't block read() if it is set.
Signed-off-by: Vasily Khoruzhick anarsoul@gmail.com --- sound/usb/line6/driver.c | 4 ++++ sound/usb/line6/driver.h | 1 + 2 files changed, 5 insertions(+)
diff --git a/sound/usb/line6/driver.c b/sound/usb/line6/driver.c index 4f096685ed65..86adf87d57f0 100644 --- a/sound/usb/line6/driver.c +++ b/sound/usb/line6/driver.c @@ -550,6 +550,7 @@ static int line6_hwdep_open(struct snd_hwdep *hw, struct file *file) /* NOTE: hwdep layer provides atomicity here */
line6->messages.active = 1; + line6->messages.nonblock = file->f_flags & O_NONBLOCK ? 1 : 0;
return 0; } @@ -579,6 +580,9 @@ line6_hwdep_read(struct snd_hwdep *hwdep, char __user *buf, long count, while (kfifo_len(&line6->messages.fifo) == 0) { mutex_unlock(&line6->messages.read_lock);
+ if (line6->messages.nonblock) + return -EAGAIN; + rv = wait_event_interruptible( line6->messages.wait_queue, kfifo_len(&line6->messages.fifo) != 0); diff --git a/sound/usb/line6/driver.h b/sound/usb/line6/driver.h index e5e572ed5f30..1a4e3700c80c 100644 --- a/sound/usb/line6/driver.h +++ b/sound/usb/line6/driver.h @@ -163,6 +163,7 @@ struct usb_line6 { struct mutex read_lock; wait_queue_head_t wait_queue; unsigned int active:1; + unsigned int nonblock:1; STRUCT_KFIFO_REC_2(LINE6_BUFSIZE_LISTEN * LINE6_RAW_MESSAGES_MAXCOUNT) fifo; } messages;
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 --- sound/usb/line6/driver.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+)
diff --git a/sound/usb/line6/driver.c b/sound/usb/line6/driver.c index 86adf87d57f0..7629116f570e 100644 --- a/sound/usb/line6/driver.c +++ b/sound/usb/line6/driver.c @@ -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 */
On Sat, 02 May 2020 21:31:18 +0200, Vasily Khoruzhick wrote:
This series adds support for polling and non-blocking read for hwdep interface. This allows apps to listen to HW events without using busy loop.
Example of app that uses hwdep interface for POD HD500 can be found here: https://github.com/anarsoul/line6_hwdep_test
Vasily Khoruzhick (2): ALSA: line6: hwdep: add support for O_NONBLOCK opening mode ALSA: line6: Add poll callback for hwdep
Looks like a nice extension. Applied both patches now to for-next branch.
thanks,
Takashi
On Sat, May 2, 2020 at 1:32 PM Takashi Iwai tiwai@suse.de wrote:
On Sat, 02 May 2020 21:31:18 +0200, Vasily Khoruzhick wrote:
This series adds support for polling and non-blocking read for hwdep interface. This allows apps to listen to HW events without using busy loop.
Example of app that uses hwdep interface for POD HD500 can be found here: https://github.com/anarsoul/line6_hwdep_test
Vasily Khoruzhick (2): ALSA: line6: hwdep: add support for O_NONBLOCK opening mode ALSA: line6: Add poll callback for hwdep
Looks like a nice extension. Applied both patches now to for-next branch.
Thanks for such a prompt response!
thanks,
Takashi
participants (2)
-
Takashi Iwai -
Vasily Khoruzhick