osdep/linux-als: support ambient-light on Linux

This implements the ambient-light property on Linux using the sysfs
interface.

.pre-commit-config.yaml

@@ -19,5 +19,5 @@ repos:
   rev: v2.3.0
   hooks:
     - id: codespell
-      args: ["--ignore-words-list", "datas,DNE,enew,HDA,numer,ontop,optionA,Paeth,pathc,inout"]
+      args: ["--ignore-words-list", "ALS,als,datas,DNE,enew,HDA,numer,ontop,optionA,Paeth,pathc,inout"]
       exclude: ^misc/language.c$

DOCS/man/input.rst

@@ -2967,7 +2967,7 @@ Property list
     Whether the window has focus. Might not be supported by all VOs.
 
 ``ambient-light``
-    Ambient lighting condition in lux. (macOS only)
+    Ambient lighting condition in lux. Only observable on macOS (macOS and Linux only)
 
 ``display-names``
     Names of the displays that the mpv window covers. On X11, these

meson.build

@@ -443,6 +443,12 @@ if posix and not darwin
     timer_source = files('osdep/timer-linux.c')
 endif
 
+if host_machine.system() == 'linux'
+    sources += files('osdep/als-linux.c')
+else
+    sources += files('osdep/als-voctrl.c')
+endif
+
 features += {'ppoll': cc.has_function('ppoll', args: '-D_GNU_SOURCE',
                                       prefix: '#include <poll.h>')}
 features += {'memrchr': cc.has_function('memrchr', args: '-D_GNU_SOURCE',

osdep/als-linux.c

@@ -0,0 +1,189 @@
+/*
+ * Linux ambient light sensor utilities
+ *
+ * This file is part of mpv.
+ *
+ * mpv is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * mpv is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with mpv.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "common/common.h"
+#include "common/global.h"
+#include "common/msg.h"
+#include "misc/bstr.h"
+#include "misc/mp_assert.h"
+#include "misc/path_utils.h"
+#include "osdep/als.h"
+#include "osdep/io.h"
+#include "player/core.h"
+#include "ta/ta_talloc.h"
+
+// For the sysfs API documentation, refer to
+//     Documentation/ABI/testing/sysfs-bus-iio
+// In Kernel tree.
+#define SYSFS_BASEDIR "/sys/bus/iio/devices"
+#define INP_RAW "in_illuminance_raw"
+#define INP_OFF "in_illuminance_offset"
+#define INP_SCL "in_illuminance_scale"
+
+struct mp_als {
+    DIR *device_dir;
+    struct mp_log *log;
+
+    // Flag we set to true if we've looked for IIO devices and found none. This
+    // way, we know that we shouldn't look again next time.
+    bool found_no_devices;
+};
+
+static void mp_als_destroy(void *p)
+{
+    struct mp_als *state = p;
+
+    if (state->device_dir) {
+        closedir(state->device_dir);
+    }
+}
+
+struct mp_als *mp_als_create(void *parent, MPContext *mpctx)
+{
+    struct mp_als *state =
+        talloc_zero(parent, struct mp_als);
+
+    state->log = mp_log_new(state, mpctx->global->log, "linux-als");
+
+    talloc_set_destructor(state, mp_als_destroy);
+
+    return state;
+}
+
+// Assumes that state->device_dir is NULL
+static int acquire_sensor(struct mp_als *state)
+{
+    mp_assert(!state->device_dir);
+    DIR *devices_dir = opendir(SYSFS_BASEDIR);
+    if (!devices_dir) {
+        MP_WARN(state,
+                "No IIO device directory in sysfs: %s\n",
+                mp_strerror(errno));
+        return -1;
+    }
+
+    void *tmp = talloc_new(NULL);
+
+    struct dirent *ent;
+    while ((ent = readdir(devices_dir))) {
+        // The directory also contains files named `trigger*` which we don't
+        // care about; only include ones for devices.
+        if (!bstr_startswith0(bstr0(ent->d_name), "iio:device"))
+            continue;
+
+        // Check if in_illuminance_raw exists so we know we have an ambient
+        // light sensor.
+        char *inp_raw_path = mp_path_join(tmp, ent->d_name, INP_RAW);
+
+        if (faccessat(dirfd(devices_dir), inp_raw_path, R_OK, 0) != 0) {
+            // Couldn't stat, continue
+            continue;
+        }
+
+        // We found an ALS
+
+        char *dev_path = mp_path_join(tmp, SYSFS_BASEDIR, ent->d_name);
+
+        state->device_dir = opendir(dev_path);
+        if (state->device_dir) {
+            MP_VERBOSE(state, "Chose ALS device %s\n", dev_path);
+            break;
+        }
+
+        MP_WARN(state, "Failed to open ambient light sensor %s: %s\n",
+                ent->d_name,
+                mp_strerror(errno));
+    }
+
+    talloc_free(tmp);
+    closedir(devices_dir);
+
+    return state->device_dir ? 0 : -1;
+}
+
+static int scan_from_subfile(struct mp_als *state,
+                             const char *subpath,
+                             const char *format,
+                             void *out)
+{
+    mp_assert(state->device_dir);
+    int fd = openat(dirfd(state->device_dir), subpath, O_RDONLY);
+    if (fd < 0)
+        return -1;
+
+    char readbuf[256];
+    ssize_t nread = read(fd, readbuf, sizeof(readbuf) - 1);
+    close(fd);
+
+    if (nread < 0)
+        return -1;
+
+    readbuf[nread] = 0;
+    return sscanf(readbuf, format, out) == 1 ? 0 : -1;
+}
+
+static int read_als_assume_have_sensor(struct mp_als *state,
+                                       double *lux)
+{
+    int illu_raw;
+    if (scan_from_subfile(state, INP_RAW, "%d", &illu_raw) < 0) {
+        MP_ERR(state,
+               "Failed to read " INP_RAW ": %s\n",
+               mp_strerror(errno));
+        return MP_ALS_STATUS_READFAILED;
+    }
+
+    double illu_off;
+    if (scan_from_subfile(state, INP_OFF, "%lf", &illu_off) < 0) {
+        MP_ERR(state,
+               "Failed to read " INP_OFF ": %s\n",
+               mp_strerror(errno));
+        return MP_ALS_STATUS_READFAILED;
+    }
+
+    double illu_scl;
+    if (scan_from_subfile(state, INP_SCL, "%lf", &illu_scl) < 0) {
+        MP_ERR(state,
+               "Failed to read " INP_SCL ": %s\n",
+               mp_strerror(errno));
+        return MP_ALS_STATUS_READFAILED;
+    }
+
+    *lux = (illu_raw + illu_off) * illu_scl;
+    return MP_ALS_STATUS_OK;
+}
+
+enum mp_als_status mp_als_get_lux(struct mp_als *state, double *lux)
+{
+    if (state->found_no_devices)
+        return MP_ALS_STATUS_NODEVICE;
+
+    if (!state->device_dir && acquire_sensor(state) < 0) {
+        state->found_no_devices = true;
+        return MP_ALS_STATUS_NODEVICE;
+    }
+
+    return read_als_assume_have_sensor(state, lux);
+}

osdep/als-voctrl.c

@@ -0,0 +1,43 @@
+/*
+ * Ambient light sensor implementation that delegates to VOCTRL_GET_AMBIENT_LUX
+ *
+ * This file is part of mpv.
+ *
+ * mpv is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * mpv is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with mpv.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+// TODO: refactor macOS implementation to not use voctrl and replace this file
+// with one for macOS.
+
+#include "osdep/als.h"
+#include "player/core.h"
+#include "ta/ta_talloc.h"
+#include "video/out/vo.h"
+
+struct mp_als {
+    MPContext *mpctx;
+};
+
+struct mp_als *mp_als_create(void *parent, MPContext *mpctx) {
+    struct mp_als *als = talloc(parent, struct mp_als);
+    *als = (struct mp_als){ .mpctx = mpctx };
+    return als;
+}
+
+enum mp_als_status mp_als_get_lux(struct mp_als *state, double *lux) {
+    struct vo *vo = state->mpctx->video_out;
+    if (!vo || vo_control(vo, VOCTRL_GET_AMBIENT_LUX, lux) < 1)
+        return MP_ALS_STATUS_NODEVICE;
+    return MP_ALS_STATUS_OK;
+}

osdep/als.h

@@ -0,0 +1,49 @@
+/*
+ * Generic interface for ambient light sensors (ALS)
+ *
+ * This file is part of mpv.
+ *
+ * mpv is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * mpv is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with mpv.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+
+#pragma once
+
+typedef struct MPContext MPContext;
+
+struct mp_als;
+
+enum mp_als_status {
+    MP_ALS_STATUS_OK = 0,
+
+    // The system has no ALS
+    MP_ALS_STATUS_NODEVICE,
+
+    // The system has an ALS, but we couldn't read it.
+    MP_ALS_STATUS_READFAILED,
+};
+
+/**
+ * @param parent talloc parent
+ * @return a newly allocated mp_linux_als_state
+ */
+// TODO: replace the mpctx parameter with mpv_global when we no longer need the
+// vo for the als-voctrl implementation.
+struct mp_als *mp_als_create(void *parent, MPContext *mpctx);
+
+/**
+ * Get the ambient brightness.
+ * @param lux output value
+ */
+enum mp_als_status mp_als_get_lux(struct mp_als *state, double *lux);

player/command.c

@@ -41,6 +41,7 @@
 #include "common/stats.h"
 #include "filters/f_decoder_wrapper.h"
 #include "command.h"
+#include "osdep/als.h"
 #include "osdep/threads.h"
 #include "osdep/timer.h"
 #include "common/common.h"
@@ -2837,12 +2838,20 @@ static int mp_property_ambient_light(void *ctx, struct m_property *prop,
                                      int action, void *arg)
 {
     MPContext *mpctx = ctx;
-    struct vo *vo = mpctx->video_out;
-    double lux;
-    if (!vo || vo_control(vo, VOCTRL_GET_AMBIENT_LUX, &lux) < 1)
-        return M_PROPERTY_UNAVAILABLE;
+    if (!mpctx->als_state) {
+        mpctx->als_state = mp_als_create(mpctx, mpctx);
+    }
 
-    return m_property_double_ro(action, arg, lux);
+    double lux;
+    switch (mp_als_get_lux(mpctx->als_state, &lux)) {
+    case MP_ALS_STATUS_OK:
+        return m_property_double_ro(action, arg, lux);
+    case MP_ALS_STATUS_NODEVICE:
+        return M_PROPERTY_UNAVAILABLE;
+    case MP_ALS_STATUS_READFAILED:
+    default:
+        return M_PROPERTY_ERROR;
+    }
 }
 
 static int mp_property_focused(void *ctx, struct m_property *prop,

player/core.h

@@ -31,6 +31,7 @@
 #include "sub/osd.h"
 #include "video/mp_image.h"
 #include "video/out/vo.h"
+#include "osdep/als.h"
 
 // definitions used internally by the core player code
 
@@ -469,6 +470,8 @@ typedef struct MPContext {
     //     to true.
     struct demuxer *open_res_demuxer;
     int open_res_error;
+
+    struct mp_als *als_state; // lazily initialized on first use
 } MPContext;
 
 // Contains information about an asynchronous work item, how it can be aborted,