ALSA: line6: hwdep: add support for O_NONBLOCK opening mode

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>
Link: https://lore.kernel.org/r/20200502193120.79115-2-anarsoul@gmail.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/sound/usb/line6/driver.c b/sound/usb/line6/driver.c
index 4f09668..86adf87 100644 (file)
--- 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 e5e572e..1a4e370 100644 (file)
--- 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;