ALSA: emu10k1: allow high-resolution mixer controls

Add a module option to allow the GPR mixer controls to have the full
resolution of the hardware, i.e., 0...2^31-1 instead of 0...100.

Because of bugs in userspace tools like alsactl and alsamixer, this is
not yet enabled by default.
Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/emu10k1/emufx.c

@@ -35,6 +35,7 @@
 #include <linux/vmalloc.h>
 #include <linux/init.h>
 #include <linux/mutex.h>
+#include <linux/moduleparam.h>
 
 #include <sound/core.h>
 #include <sound/tlv.h>
@@ -50,6 +51,10 @@
 #define EMU10K1_CENTER_LFE_FROM_FRONT
 #endif
 
+static bool high_res_gpr_volume;
+module_param(high_res_gpr_volume, bool, 0444);
+MODULE_PARM_DESC(high_res_gpr_volume, "GPR mixer controls use 31-bit range.");
+
 /*
  *  Tables
  */ 
@@ -296,6 +301,7 @@ static const u32 db_table[101] = {
 
 /* EMU10k1/EMU10k2 DSP control db gain */
 static const DECLARE_TLV_DB_SCALE(snd_emu10k1_db_scale1, -4000, 40, 1);
+static const DECLARE_TLV_DB_LINEAR(snd_emu10k1_db_linear, TLV_DB_GAIN_MUTE, 0);
 
 static const u32 onoff_table[2] = {
 	0x00000000, 0x00000001
@@ -1072,10 +1078,17 @@ snd_emu10k1_init_mono_control(struct snd_emu10k1_fx8010_control_gpr *ctl,
 	strcpy(ctl->id.name, name);
 	ctl->vcount = ctl->count = 1;
 	ctl->gpr[0] = gpr + 0; ctl->value[0] = defval;
+	if (high_res_gpr_volume) {
+		ctl->min = 0;
+		ctl->max = 0x7fffffff;
+		ctl->tlv = snd_emu10k1_db_linear;
+		ctl->translation = EMU10K1_GPR_TRANSLATION_NONE;
+	} else {
 		ctl->min = 0;
 		ctl->max = 100;
 		ctl->tlv = snd_emu10k1_db_scale1;
 		ctl->translation = EMU10K1_GPR_TRANSLATION_TABLE100;
+	}
 }
 
 static void __devinit
@@ -1087,10 +1100,17 @@ snd_emu10k1_init_stereo_control(struct snd_emu10k1_fx8010_control_gpr *ctl,
 	ctl->vcount = ctl->count = 2;
 	ctl->gpr[0] = gpr + 0; ctl->value[0] = defval;
 	ctl->gpr[1] = gpr + 1; ctl->value[1] = defval;
+	if (high_res_gpr_volume) {
+		ctl->min = 0;
+		ctl->max = 0x7fffffff;
+		ctl->tlv = snd_emu10k1_db_linear;
+		ctl->translation = EMU10K1_GPR_TRANSLATION_NONE;
+	} else {
 		ctl->min = 0;
 		ctl->max = 100;
 		ctl->tlv = snd_emu10k1_db_scale1;
 		ctl->translation = EMU10K1_GPR_TRANSLATION_TABLE100;
+	}
 }
 
 static void __devinit