From 9e760b6e80a875f0a9f3f520bf9656e274b7eb81 Mon Sep 17 00:00:00 2001

From: Lennart Poettering <lennart@poettering.net>

Date: Mon, 14 Oct 2013 02:12:52 +0200

Subject: [PATCH] backlight: always prefer "firmware"/"platform" backlights

 over "raw" backlights if we have both for the same device

(cherry picked from commit 0f4ba83c397e807939a4eb0b2cbd04ad4ab548cc)

Conflicts:

	rules/99-systemd.rules.in

https://bugzilla.redhat.com/show_bug.cgi?id=1108019

---

 rules/99-systemd.rules.in |   6 +-

 src/backlight/backlight.c | 222 +++++++++++++++++++++++++++++++++++++++++++---

 2 files changed, 212 insertions(+), 16 deletions(-)

diff --git a/rules/99-systemd.rules.in b/rules/99-systemd.rules.in

index 79a03cd227..ff0e771132 100644

--- a/rules/99-systemd.rules.in

+++ b/rules/99-systemd.rules.in

@@ -54,10 +54,10 @@ SUBSYSTEM=="usb", ENV{DEVTYPE}=="usb_device", ENV{ID_USB_INTERFACES}=="*:0701??:

 ACTION=="add", SUBSYSTEM=="net", KERNEL!="lo", RUN+="@rootlibexecdir@/systemd-sysctl --prefix=/proc/sys/net/ipv4/conf/$name --prefix=/proc/sys/net/ipv4/neigh/$name --prefix=/proc/sys/net/ipv6/conf/$name --prefix=/proc/sys/net/ipv6/neigh/$name"

-# Pull in backlight save/restore for all firmware backlight devices,

-# and keyboard backlights

+# Pull in backlight save/restore for all backlight devices and

+# keyboard backlights

-SUBSYSTEM=="backlight", ATTR{type}=="firmware", TAG+="systemd", ENV{SYSTEMD_WANTS}+="systemd-backlight@$name.service"

+SUBSYSTEM=="backlight", TAG+="systemd", ENV{SYSTEMD_WANTS}+="systemd-backlight@$name.service"

 SUBSYSTEM=="leds", KERNEL=="*kbd_backlight", TAG+="systemd", ENV{SYSTEMD_WANTS}+="systemd-backlight@$name.service"

 # Asynchronously mount file systems implemented by these modules as

diff --git a/src/backlight/backlight.c b/src/backlight/backlight.c

index c45b2d0b6b..51a67a042a 100644

--- a/src/backlight/backlight.c

+++ b/src/backlight/backlight.c

@@ -25,10 +25,178 @@

 #include "libudev.h"

 #include "udev-util.h"

+static struct udev_device *find_pci_or_platform_parent(struct udev_device *device) {

+        struct udev_device *parent;

+        const char *subsystem, *sysname;

+

+        assert(device);

+

+        parent = udev_device_get_parent(device);

+        if (!parent)

+                return NULL;

+

+        subsystem = udev_device_get_subsystem(parent);

+        if (!subsystem)

+                return NULL;

+

+        sysname = udev_device_get_sysname(parent);

+        if (!sysname)

+                return NULL;

+

+        if (streq(subsystem, "drm")) {

+                const char *c;

+

+                c = startswith(sysname, "card");

+                if (!c)

+                        return NULL;

+

+                c += strspn(c, "0123456789");

+                if (*c == '-') {

+                        /* A connector DRM device, let's ignore all but LVDS and eDP! */

+

+                        if (!startswith(c, "-LVDS-") &&

+                            !startswith(c, "-Embedded DisplayPort-"))

+                                return NULL;

+                }

+

+        } else if (streq(subsystem, "pci")) {

+                const char *value;

+

+                value = udev_device_get_sysattr_value(parent, "class");

+                if (value) {

+                        unsigned long class;

+

+                        if (safe_atolu(value, &class) < 0) {

+                                log_warning("Cannot parse PCI class %s of device %s:%s.", value, subsystem, sysname);

+                                return NULL;

+                        }

+

+                        /* Graphics card */

+                        if (class == 0x30000)

+                                return parent;

+                }

+

+        } else if (streq(subsystem, "platform"))

+                return parent;

+

+        return find_pci_or_platform_parent(parent);

+}

+

+static bool same_device(struct udev_device *a, struct udev_device *b) {

+        assert(a);

+        assert(b);

+

+        if (!streq_ptr(udev_device_get_subsystem(a), udev_device_get_subsystem(b)))

+                return false;

+

+        if (!streq_ptr(udev_device_get_sysname(a), udev_device_get_sysname(b)))

+                return false;

+

+        return true;

+}

+

+static bool validate_device(struct udev *udev, struct udev_device *device) {

+        _cleanup_udev_enumerate_unref_ struct udev_enumerate *enumerate = NULL;

+        struct udev_list_entry *item = NULL, *first = NULL;

+        struct udev_device *parent;

+        const char *v, *subsystem;

+        int r;

+

+        assert(udev);

+        assert(device);

+

+        /* Verify whether we should actually care for a specific

+         * backlight device. For backlight devices there might be

+         * multiple ways to access the same control: "firmware"

+         * (i.e. ACPI), "platform" (i.e. via the machine's EC) and

+         * "raw" (via the graphics card). In general we should prefer

+         * "firmware" (i.e. ACPI) or "platform" access over "raw"

+         * access, in order not to confuse the BIOS/EC, and

+         * compatibility with possible low-level hotkey handling of

+         * screen brightness. The kernel will already make sure to

+         * expose only one of "firmware" and "platform" for the same

+         * device to userspace. However, we still need to make sure

+         * that we use "raw" only if no "firmware" or "platform"

+         * device for the same device exists. */

+

+        subsystem = udev_device_get_subsystem(device);

+        if (!streq_ptr(subsystem, "backlight"))

+                return true;

+

+        v = udev_device_get_sysattr_value(device, "type");

+        if (!streq_ptr(v, "raw"))

+                return true;

+

+        parent = find_pci_or_platform_parent(device);

+        if (!parent)

+                return true;

+

+        subsystem = udev_device_get_subsystem(parent);

+        if (!subsystem)

+                return true;

+

+        enumerate = udev_enumerate_new(udev);

+        if (!enumerate)

+                return true;

+

+        r = udev_enumerate_add_match_subsystem(enumerate, "backlight");

+        if (r < 0)

+                return true;

+

+        r = udev_enumerate_scan_devices(enumerate);

+        if (r < 0)

+                return true;

+

+        first = udev_enumerate_get_list_entry(enumerate);

+        udev_list_entry_foreach(item, first) {

+                _cleanup_udev_device_unref_ struct udev_device *other;

+                struct udev_device *other_parent;

+                const char *other_subsystem;

+

+                other = udev_device_new_from_syspath(udev, udev_list_entry_get_name(item));

+                if (!other)

+                        return true;

+

+                if (same_device(device, other))

+                        continue;

+

+                v = udev_device_get_sysattr_value(other, "type");

+                if (!streq_ptr(v, "platform") && !streq_ptr(v, "firmware"))

+                        continue;

+

+                /* OK, so there's another backlight device, and it's a

+                 * platform or firmware device, so, let's see if we

+                 * can verify it belongs to the same device as

+                 * ours. */

+                other_parent = find_pci_or_platform_parent(other);

+                if (!other_parent)

+                        continue;

+

+                if (same_device(parent, other_parent)) {

+                        /* Both have the same PCI parent, that means

+                         * we are out. */

+                        log_debug("Skipping backlight device %s, since backlight device %s is on same PCI device and, takes precedence.", udev_device_get_sysname(device), udev_device_get_sysname(other));

+                        return false;

+                }

+

+                other_subsystem = udev_device_get_subsystem(other_parent);

+                if (streq_ptr(other_subsystem, "platform") && streq_ptr(subsystem, "pci")) {

+                        /* The other is connected to the platform bus

+                         * and we are a PCI device, that also means we

+                         * are out. */

+                        log_debug("Skipping backlight device %s, since backlight device %s is a platform device and takes precedence.", udev_device_get_sysname(device), udev_device_get_sysname(other));

+                        return false;

+                }

+        }

+

+        return true;

+}

+

 int main(int argc, char *argv[]) {

         _cleanup_udev_unref_ struct udev *udev = NULL;

         _cleanup_udev_device_unref_ struct udev_device *device = NULL;

-        _cleanup_free_ char *saved = NULL;

+        _cleanup_free_ char *saved = NULL, *ss = NULL;

+        const char *sysname;

         int r;

         if (argc != 3) {

@@ -54,34 +222,57 @@ int main(int argc, char *argv[]) {

                 return EXIT_FAILURE;

         }

+        sysname = strchr(argv[2], ':');

+        if (!sysname) {

+                log_error("Requires pair of subsystem and sysname for specifying backlight device.");

+                return EXIT_FAILURE;

+        }

+

+        ss = strndup(argv[2], sysname - argv[2]);

+        if (!ss) {

+                log_oom();

+                return EXIT_FAILURE;

+        }

+

+        sysname++;

+

+        if (!streq(ss, "backlight") && !streq(ss, "leds")) {

+                log_error("Not a backlight or LED device: '%s:%s'", ss, sysname);

+                return EXIT_FAILURE;

+        }

+

         errno = 0;

-        device = udev_device_new_from_subsystem_sysname(udev, "backlight", argv[2]);

-        if (!device)

-                device = udev_device_new_from_subsystem_sysname(udev, "leds", argv[2]);

+        device = udev_device_new_from_subsystem_sysname(udev, ss, sysname);

         if (!device) {

                 if (errno != 0)

-                        log_error("Failed to get backlight device '%s': %m", argv[2]);

+                        log_error("Failed to get backlight or LED device '%s:%s': %m", ss, sysname);

                 else

-                        r = log_oom();

-

-                return EXIT_FAILURE;

-        }

+                        log_oom();

-        if (!streq_ptr(udev_device_get_subsystem(device), "backlight") &&

-            !streq_ptr(udev_device_get_subsystem(device), "leds")) {

-                log_error("Not a backlight device: %s", argv[2]);

                 return EXIT_FAILURE;

         }

-        saved = strappend("/var/lib/systemd/backlight/", udev_device_get_sysname(device));

+        saved = strjoin("/var/lib/systemd/backlight/", ss, ":", sysname, NULL);

         if (!saved) {

                 log_oom();

                 return EXIT_FAILURE;

         }

+        /* If there are multiple conflicting backlight devices, then

+         * their probing at boot-time might happen in any order. This

+         * means the validity checking of the device then is not

+         * reliable, since it might not see other devices conflicting

+         * with a specific backlight. To deal with this we will

+         * actively delete backlight state files at shutdown (where

+         * device probing should be complete), so that the validity

+         * check at boot time doesn't have to be reliable. */

+

         if (streq(argv[1], "load")) {

                 _cleanup_free_ char *value = NULL;

+                if (!validate_device(udev, device))

+                        return EXIT_SUCCESS;

+

                 r = read_one_line_file(saved, &value);

                 if (r < 0) {

@@ -101,6 +292,11 @@ int main(int argc, char *argv[]) {

         } else if (streq(argv[1], "save")) {

                 const char *value;

+                if (!validate_device(udev, device)) {

+                        unlink(saved);

+                        return EXIT_SUCCESS;

+                }

+

                 value = udev_device_get_sysattr_value(device, "brightness");

                 if (!value) {

                         log_error("Failed to read system attribute: %s", strerror(-r));