backlight: Amalgamate hardcoded priority tables

Our fallback path for finding the backlight interface uses a hardcoded
table of known backlight controllers in proirity order. Rather than
maintain this table twice in the midst of the KMS logic, push it to the
new set of common backlight routines.

This incorporates bugfixes from SNA to handle unknown backlights, but
usable, gracefully.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

1 files changed, 139 insertions, 26 deletions

diff --git a/src/backlight.c b/src/backlight.c
index b04b5f79..5011cb86 100644
--- a/src/backlight.c
+++ b/src/backlight.c
@@ -29,21 +29,31 @@
 #include "config.h"
 #endif
 
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <sys/stat.h>
+
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
+#include <ctype.h>
+#include <limits.h>
 #include <fcntl.h>
 #include <unistd.h>
-#include <string.h>
-#include <sys/types.h>
-#include <sys/wait.h>
-#include <sys/stat.h>
+#include <dirent.h>
 
 #include "backlight.h"
 #include "fd.h"
 
+#define BACKLIGHT_CLASS "/sys/class/backlight"
+
 /* Enough for 10 digits of backlight + '\n' + '\0' */
 #define BACKLIGHT_VALUE_LEN 12
 
+#ifndef ARRAY_SIZE
+#define ARRAY_SIZE(A) (sizeof(A)/sizeof(A[0]))
+#endif
+
 /*
  * Unfortunately this is not as simple as I would like it to be. If selinux is
  * dropping dbus messages pkexec may block *forever*.
@@ -110,6 +120,7 @@ int backlight_open(struct backlight *b, char *iface)
 
 	b->max = param.max;
 	b->fd = -1;
+	b->type = BL_PLATFORM;
 
 	return param.curval;
 }
@@ -124,23 +135,38 @@ is_sysfs_fd(int fd)
 }
 
 static int
-__backlight_read(const char *iface, const char *file)
+__backlight_open(const char *iface, const char *file, int mode)
 {
 	char buf[1024];
-	int fd, val;
+	int fd;
 
 	snprintf(buf, sizeof(buf), "%s/%s/%s", BACKLIGHT_CLASS, iface, file);
-	fd = open(buf, O_RDONLY);
+	fd = open(buf, mode);
 	if (fd == -1)
 		return -1;
 
-	if (is_sysfs_fd(fd)) {
-		val = read(fd, buf, BACKLIGHT_VALUE_LEN - 1);
-		if (val > 0) {
-			buf[val] = '\0';
-			val = atoi(buf);
-		} else
-			val = -1;
+	if (!is_sysfs_fd(fd)) {
+		close(fd);
+		return -1;
+	}
+
+	return fd;
+}
+
+static int
+__backlight_read(const char *iface, const char *file)
+{
+	char buf[BACKLIGHT_VALUE_LEN];
+	int fd, val;
+
+	fd = __backlight_open(iface, file, O_RDONLY);
+	if (fd < 0)
+		return -1;
+
+	val = read(fd, buf, BACKLIGHT_VALUE_LEN - 1);
+	if (val > 0) {
+		buf[val] = '\0';
+		val = atoi(buf);
 	} else
 		val = -1;
 	close(fd);
@@ -148,15 +174,71 @@ __backlight_read(const char *iface, const char *file)
 	return val;
 }
 
-int backlight_exists(const char *iface)
+/* List of available kernel interfaces in priority order */
+static const char *known_interfaces[] = {
+	"dell_backlight",
+	"gmux_backlight",
+	"asus-laptop",
+	"asus-nb-wmi",
+	"eeepc",
+	"thinkpad_screen",
+	"mbp_backlight",
+	"fujitsu-laptop",
+	"sony",
+	"samsung",
+	"acpi_video1",
+	"acpi_video0",
+	"intel_backlight",
+};
+
+static enum backlight_type __backlight_type(const char *iface)
+{
+	char buf[1024];
+	int fd, v;
+
+	v = -1;
+	fd = __backlight_open(iface, "type", O_RDONLY);
+	if (fd >= 0) {
+		v = read(fd, buf, sizeof(buf)-1);
+		close(fd);
+	}
+	if (v > 0) {
+		while (v > 0 && isspace(buf[v-1]))
+			v--;
+		buf[v] = '\0';
+
+		if (strcmp(buf, "raw") == 0)
+			v = BL_RAW;
+		else if (strcmp(buf, "platform") == 0)
+			v = BL_PLATFORM;
+		else if (strcmp(buf, "firmware") == 0)
+			v = BL_FIRMWARE;
+		else
+			v = BL_NAMED;
+	} else
+		v = BL_NAMED;
+
+	if (v == BL_NAMED) {
+		int i;
+		for (i = 0; i < ARRAY_SIZE(known_interfaces); i++) {
+			if (strcmp(iface, known_interfaces[i]) == 0)
+				break;
+		}
+		v += i;
+	}
+
+	return v;
+}
+
+enum backlight_type backlight_exists(const char *iface)
 {
 	if (__backlight_read(iface, "brightness") < 0)
-		return 0;
+		return BL_NONE;
 
 	if (__backlight_read(iface, "max_brightness") <= 0)
-		return 0;
+		return BL_NONE;
 
-	return 1;
+	return __backlight_type(iface);
 }
 
 static int __backlight_init(struct backlight *b, char *iface, int fd)
@@ -168,19 +250,12 @@ static int __backlight_init(struct backlight *b, char *iface, int fd)
 
 static int __backlight_direct_init(struct backlight *b, char *iface)
 {
-	char path[1024];
 	int fd;
 
-	snprintf(path, sizeof(path), "%s/%s/brightness", BACKLIGHT_CLASS, iface);
-	fd = open(path, O_RDWR);
+	fd = __backlight_open(iface, "brightness", O_RDWR);
 	if (fd < 0)
 		return 0;
 
-	if (!is_sysfs_fd(fd)) {
-		close(fd);
-		return 0;
-	}
-
 	return __backlight_init(b, iface, fd);
 }
 
@@ -242,13 +317,51 @@ static int __backlight_helper_init(struct backlight *b, char *iface)
 #endif
 }
 
+static char *
+__backlight_find(void)
+{
+	char *best_iface = NULL;
+	unsigned best_type = INT_MAX;
+	DIR *dir;
+	struct dirent *de;
+
+	dir = opendir(BACKLIGHT_CLASS);
+	if (dir == NULL)
+		return NULL;
+
+	while ((de = readdir(dir))) {
+		int v;
+
+		if (*de->d_name == '.')
+			continue;
+
+		/* Fallback to priority list of known iface for old kernels */
+		v = backlight_exists(de->d_name);
+		if (v < best_type) {
+			char *copy = strdup(de->d_name);
+			if (copy) {
+				free(best_iface);
+				best_iface = copy;
+				best_type = v;
+			}
+		}
+	}
+	closedir(dir);
+
+	return best_iface;
+}
+
 int backlight_open(struct backlight *b, char *iface)
 {
 	int level;
 
 	if (iface == NULL)
+		iface = __backlight_find();
+	if (iface == NULL)
 		return -1;
 
+	b->type = __backlight_type(iface);
+
 	b->max = __backlight_read(iface, "max_brightness");
 	if (b->max <= 0)
 		return -1;