ALSA: hda - Get rid of magic digits for subdev hack

Define a proper const for a magic 31bit flag for subdev / NID setup
with a brief comment.

Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 12 insertions, 3 deletions

diff --git a/sound/pci/hda/hda_local.h b/sound/pci/hda/hda_local.h
index 3bfcf42ff6cf..4e77f4747291 100644
--- a/sound/pci/hda/hda_local.h
+++ b/sound/pci/hda/hda_local.h
@@ -23,6 +23,15 @@
 #ifndef __SOUND_HDA_LOCAL_H
 #define __SOUND_HDA_LOCAL_H
 
+/* We abuse kcontrol_new.subdev field to pass the NID corresponding to
+ * the given new control.  If id.subdev has a bit flag HDA_SUBDEV_NID_FLAG,
+ * snd_hda_ctl_add() takes the lower-bit subdev value as a valid NID.
+ * 
+ * Note that the subdevice field is cleared again before the real registration
+ * in snd_hda_ctl_add(), so that this value won't appear in the outside.
+ */
+#define HDA_SUBDEV_NID_FLAG     (1U << 31)
+
 /*
  * for mixer controls
  */
@@ -33,7 +42,7 @@
 /* mono volume with index (index=0,1,...) (channel=1,2) */
 #define HDA_CODEC_VOLUME_MONO_IDX(xname, xcidx, nid, channel, xindex, direction) \
         { .iface = SNDRV_CTL_ELEM_IFACE_MIXER, .name = xname, .index = xcidx,  \
-          .subdevice = (1<<31)|(nid), \
+          .subdevice = HDA_SUBDEV_NID_FLAG | (nid), \
           .access = SNDRV_CTL_ELEM_ACCESS_READWRITE | \
                     SNDRV_CTL_ELEM_ACCESS_TLV_READ | \
                     SNDRV_CTL_ELEM_ACCESS_TLV_CALLBACK, \
@@ -54,7 +63,7 @@
 /* mono mute switch with index (index=0,1,...) (channel=1,2) */
 #define HDA_CODEC_MUTE_MONO_IDX(xname, xcidx, nid, channel, xindex, direction) \
         { .iface = SNDRV_CTL_ELEM_IFACE_MIXER, .name = xname, .index = xcidx, \
-          .subdevice = (1<<31)|(nid), \
+          .subdevice = HDA_SUBDEV_NID_FLAG | (nid), \
           .info = snd_hda_mixer_amp_switch_info, \
           .get = snd_hda_mixer_amp_switch_get, \
           .put = snd_hda_mixer_amp_switch_put, \
@@ -71,7 +80,7 @@
 /* special beep mono mute switch with index (index=0,1,...) (channel=1,2) */
 #define HDA_CODEC_MUTE_BEEP_MONO_IDX(xname, xcidx, nid, channel, xindex, direction) \
         { .iface = SNDRV_CTL_ELEM_IFACE_MIXER, .name = xname, .index = xcidx, \
-          .subdevice = (1<<31)|(nid), \
+          .subdevice = HDA_SUBDEV_NID_FLAG | (nid), \
           .info = snd_hda_mixer_amp_switch_info, \
           .get = snd_hda_mixer_amp_switch_get, \
           .put = snd_hda_mixer_amp_switch_put_beep, \