[hackers] [PATCH] volume: compute volume by alsa api on linux

From: Doan Tran Cong Danh <congdanhqx_AT_gmail.com>
Date: Tue, 2 Apr 2019 07:01:45 +0700

From: Đoàn Trần Công Danh <congdanhqx_AT_gmail.com>

There's a non-posix assignment inside config.mk,
but it's supported with both gmake and bmake.

    var != shell command

---
 components/volume.c | 59 +++++++++++++++++++++++++++++++++++++++++++++
 config.def.h        |  1 +
 config.mk           |  3 ++-
 3 files changed, 62 insertions(+), 1 deletion(-)
diff --git a/components/volume.c b/components/volume.c
index 61cec90..eeb3975 100644
--- a/components/volume.c
+++ b/components/volume.c
_AT_@ -1,5 +1,6 @@
 /* See LICENSE file for copyright and license details. */
 #include <fcntl.h>
+#include <limits.h>
 #include <stdio.h>
 #include <string.h>
 #include <sys/ioctl.h>
_AT_@ -72,6 +73,64 @@
 
 		return bprintf("%d", m ? 0 : v * 100 / 255);
 	}
+#elif defined(__linux__)
+#include <alsa/asoundlib.h>
+#include <alsa/control.h>
+
+#define SOUND_CARD "default"
+#define MIXER_IDX 0
+
+const char*
+vol_perc(const char *mixer)
+{
+	snd_mixer_t* handle;
+	snd_mixer_elem_t* elem;
+	snd_mixer_selem_id_t* sid;
+	snd_mixer_selem_channel_id_t c;
+
+	int emute, muted = 0;
+	long minv, maxv, elemv, vol = LONG_MIN;
+	const char *result = NULL;
+
+	snd_mixer_selem_id_alloca(&sid);
+
+	//sets simple-mixer index and name
+	snd_mixer_selem_id_set_index(sid, MIXER_IDX);
+	snd_mixer_selem_id_set_name(sid, mixer);
+
+	if ((snd_mixer_open(&handle, 0)) < 0)
+		goto out;
+	if (snd_mixer_attach(handle, SOUND_CARD) < 0 ||
+	    snd_mixer_selem_register(handle, NULL, NULL) < 0 ||
+	    snd_mixer_load(handle) < 0 ||
+	    !(elem = snd_mixer_find_selem(handle, sid)))
+		goto cleanup;
+
+	snd_mixer_selem_get_playback_volume_range(elem, &minv, &maxv);
+
+	if(minv == maxv)
+		goto cleanup;
+
+	for (c = 0; c <= SND_MIXER_SCHN_LAST; ++c)
+		if (snd_mixer_selem_has_playback_channel(elem, c)) {
+			if (!snd_mixer_selem_get_playback_volume(elem, c, &elemv)
+			    && elemv > vol)
+				vol = elemv;
+			if (!muted
+			    && !snd_mixer_selem_get_playback_switch(elem, c, &emute))
+				muted = !emute;
+		}
+	if (minv > vol || maxv < vol)
+		goto cleanup;
+
+	result = bprintf("%d%% [%s]",
+			 (200 * (vol - minv) + maxv - minv) / (maxv - minv) / 2,
+			 muted ? "off" : "on");
+cleanup:
+	snd_mixer_close(handle);
+out:
+	return result;
+}
 #else
 	#include <sys/soundcard.h>
 
diff --git a/config.def.h b/config.def.h
index e06be66..40f0a28 100644
--- a/config.def.h
+++ b/config.def.h
_AT_@ -58,6 +58,7 @@ static const char unknown_str[] = "n/a";
  * uptime              system uptime                   NULL
  * username            username of current user        NULL
  * vol_perc            OSS/ALSA volume in percent      mixer file (/dev/mixer)
+ *                                                     mixer name on Linux (Master)
  * wifi_perc           WiFi signal in percent          interface name (wlan0)
  * wifi_essid          WiFi ESSID                      interface name (wlan0)
  */
diff --git a/config.mk b/config.mk
index 3b32b7c..6903fe1 100644
--- a/config.mk
+++ b/config.mk
_AT_@ -14,7 +14,8 @@ X11LIB = /usr/X11R6/lib
 CPPFLAGS = -I$(X11INC) -D_DEFAULT_SOURCE
 CFLAGS   = -std=c99 -pedantic -Wall -Wextra -Os
 LDFLAGS  = -L$(X11LIB) -s
-LDLIBS   = -lX11
+ALSALIBS != [ Linux = `uname -s` ] && printf "%s" "-lasound"
+LDLIBS   = -lX11 $(ALSALIBS)
 
 # compiler and linker
 CC = cc
-- 
2.21.0

Received on Tue Apr 02 2019 - 02:01:45 CEST