ALSA: firewire-tascam: add new hwdep ioctl command to get state image

In a previous commit, ALSA firewire-tascam driver stores state image
from tx isochronous packets. This image includes states of knob, fader,
button of control surface, level of gain/volume of each physical
inputs/outputs, and so on. It's useful for userspace applications to
read whole of the image.

This commit adds a unique ioctl command for ALSA hwdep interface for the
purpose. For actual meaning of each bits in this image, please refer to
discussion in alsa-devel[1].

[1] http://mailman.alsa-project.org/pipermail/alsa-devel/2018-October/140785.html

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 10 insertions, 0 deletions

diff --git a/sound/firewire/tascam/tascam-hwdep.c b/sound/firewire/tascam/tascam-hwdep.c
index 4e4c1e9020e8..a80397116c48 100644
--- a/sound/firewire/tascam/tascam-hwdep.c
+++ b/sound/firewire/tascam/tascam-hwdep.c
@@ -123,6 +123,14 @@ static int hwdep_unlock(struct snd_tscm *tscm)
         return err;
 }
 
+static int tscm_hwdep_state(struct snd_tscm *tscm, void __user *arg)
+{
+        if (copy_to_user(arg, tscm->state, sizeof(tscm->state)))
+                return -EFAULT;
+
+        return 0;
+}
+
 static int hwdep_release(struct snd_hwdep *hwdep, struct file *file)
 {
         struct snd_tscm *tscm = hwdep->private_data;
@@ -147,6 +155,8 @@ static int hwdep_ioctl(struct snd_hwdep *hwdep, struct file *file,
                 return hwdep_lock(tscm);
         case SNDRV_FIREWIRE_IOCTL_UNLOCK:
                 return hwdep_unlock(tscm);
+        case SNDRV_FIREWIRE_IOCTL_TASCAM_STATE:
+                return tscm_hwdep_state(tscm, (void __user *)arg);
         default:
                 return -ENOIOCTLCMD;
         }