Merge tag 'tags/mute-led-rework' into for-next

ALSA: control - add generic LED API

This patchset tries to resolve the diversity in the audio LED
control among the ALSA drivers. A new control layer registration
is introduced which allows to run additional operations on
top of the elementary ALSA sound controls.

A new control access group (three bits in the access flags)
was introduced to carry the LED group information for
the sound controls. The low-level sound drivers can just
mark those controls using this access group. This information
is not exported to the user space, but user space can
manage the LED sound control associations through sysfs
(last patch) per Mark's request. It makes things fully
configurable in the kernel and user space (UCM).

The actual state ('route') evaluation is really easy
(the minimal value check for all channels / controls / cards).
If there's more complicated logic for a given hardware,
the card driver may eventually export a new read-only
sound control for the LED group and do the logic itself.

The new LED trigger control code is completely separated
and possibly optional (there's no symbol dependency).
The full code separation allows eventually to move this
LED trigger control to the user space in future.
Actually it replaces the already present functionality
in the kernel space (HDA drivers) and allows a quick adoption
for the recent hardware (ASoC codecs including SoundWire).

snd_ctl_led            24576  0

The sound driver implementation is really easy:

1) call snd_ctl_led_request() when control LED layer should be
   automatically activated
   / it calls module_request("snd-ctl-led") on demand /
2) mark all related kcontrols with
        SNDRV_CTL_ELEM_ACCESS_SPK_LED or
        SNDRV_CTL_ELEM_ACCESS_MIC_LED

Link: https://lore.kernel.org/r/20210317172945.842280-1-perex@perex.cz
Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 12 insertions, 4 deletions

diff --git a/drivers/usb/class/usblp.c b/drivers/usb/class/usblp.c
index c9f6e9758288..f27b4aecff3d 100644
--- a/drivers/usb/class/usblp.c
+++ b/drivers/usb/class/usblp.c
@@ -494,16 +494,24 @@ static int usblp_release(struct inode *inode, struct file *file)
 /* No kernel lock - fine */
 static __poll_t usblp_poll(struct file *file, struct poll_table_struct *wait)
 {
-	__poll_t ret;
+	struct usblp *usblp = file->private_data;
+	__poll_t ret = 0;
 	unsigned long flags;
 
-	struct usblp *usblp = file->private_data;
 	/* Should we check file->f_mode & FMODE_WRITE before poll_wait()? */
 	poll_wait(file, &usblp->rwait, wait);
 	poll_wait(file, &usblp->wwait, wait);
+
+	mutex_lock(&usblp->mut);
+	if (!usblp->present)
+		ret |= EPOLLHUP;
+	mutex_unlock(&usblp->mut);
+
 	spin_lock_irqsave(&usblp->lock, flags);
-	ret = ((usblp->bidir && usblp->rcomplete) ? EPOLLIN  | EPOLLRDNORM : 0) |
-	   ((usblp->no_paper || usblp->wcomplete) ? EPOLLOUT | EPOLLWRNORM : 0);
+	if (usblp->bidir && usblp->rcomplete)
+		ret |= EPOLLIN  | EPOLLRDNORM;
+	if (usblp->no_paper || usblp->wcomplete)
+		ret |= EPOLLOUT | EPOLLWRNORM;
 	spin_unlock_irqrestore(&usblp->lock, flags);
 	return ret;
 }