ALSA: Add new TLV types for dBwith min/max

Add new types for TLV dB scale specified with min/max values instead
of min/step since the resolution can't match always with the one
a device provides.  For example, usb audio devices give 1/256 dB
resolution while ALSA TLV is based on 1/100 dB resolution.
The new min/max types have less problems because the possible
rounding error happens only at min/max.

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

include/sound/tlv.h

@@ -35,13 +35,27 @@
 #define SNDRV_CTL_TLVT_DB_SCALE	1       /* dB scale */
 #define SNDRV_CTL_TLVT_DB_LINEAR 2	/* linear volume */
 #define SNDRV_CTL_TLVT_DB_RANGE 3	/* dB range container */
+#define SNDRV_CTL_TLVT_DB_MINMAX 4	/* dB scale with min/max */
+#define SNDRV_CTL_TLVT_DB_MINMAX_MUTE 5	/* dB scale with min/max with mute */
 
 #define TLV_DB_SCALE_ITEM(min, step, mute)			\
 	SNDRV_CTL_TLVT_DB_SCALE, 2 * sizeof(unsigned int),	\
 	(min), ((step) & 0xffff) | ((mute) ? 0x10000 : 0)
 #define DECLARE_TLV_DB_SCALE(name, min, step, mute) \
 	unsigned int name[] = { TLV_DB_SCALE_ITEM(min, step, mute) }
 
+/* dB scale specified with min/max values instead of step */
+#define TLV_DB_MINMAX_ITEM(min_dB, max_dB)			\
+	SNDRV_CTL_TLVT_DB_MINMAX, 2 * sizeof(unsigned int),	\
+	(min_dB), (max_dB)
+#define TLV_DB_MINMAX_MUTE_ITEM(min_dB, max_dB)			\
+	SNDRV_CTL_TLVT_DB_MINMAX_MUTE, 2 * sizeof(unsigned int),	\
+	(min_dB), (max_dB)
+#define DECLARE_TLV_DB_MINMAX(name, min_dB, max_dB) \
+	unsigned int name[] = { TLV_DB_MINMAX_ITEM(min_dB, max_dB) }
+#define DECLARE_TLV_DB_MINMAX_MUTE(name, min_dB, max_dB) \
+	unsigned int name[] = { TLV_DB_MINMAX_MUTE_ITEM(min_dB, max_dB) }
+
 /* linear volume between min_dB and max_dB (.01dB unit) */
 #define TLV_DB_LINEAR_ITEM(min_dB, max_dB)		    \
 	SNDRV_CTL_TLVT_DB_LINEAR, 2 * sizeof(unsigned int), \

sound/core/vmaster.c

@@ -353,7 +353,8 @@ static void master_free(struct snd_kcontrol *kcontrol)
  *
  * The optional argument @tlv can be used to specify the TLV information
  * for dB scale of the master control.  It should be a single element
- * with #SNDRV_CTL_TLVT_DB_SCALE type, and should be the max 0dB.
+ * with #SNDRV_CTL_TLVT_DB_SCALE, #SNDRV_CTL_TLV_DB_MINMAX or
+ * #SNDRV_CTL_TLVT_DB_MINMAX_MUTE type, and should be the max 0dB.
  */
 struct snd_kcontrol *snd_ctl_make_virtual_master(char *name,
 						 const unsigned int *tlv)
@@ -384,7 +385,10 @@ struct snd_kcontrol *snd_ctl_make_virtual_master(char *name,
 	kctl->private_free = master_free;
 
 	/* additional (constant) TLV read */
-	if (tlv && tlv[0] == SNDRV_CTL_TLVT_DB_SCALE) {
+	if (tlv &&
+	    (tlv[0] == SNDRV_CTL_TLVT_DB_SCALE ||
+	     tlv[0] == SNDRV_CTL_TLVT_DB_MINMAX ||
+	     tlv[0] == SNDRV_CTL_TLVT_DB_MINMAX_MUTE)) {
 		kctl->vd[0].access |= SNDRV_CTL_ELEM_ACCESS_TLV_READ;
 		memcpy(master->tlv, tlv, sizeof(master->tlv));
 		kctl->tlv.p = master->tlv;