intel: Add a helper for setting backlight without root rights

Once the xserver stops running as root on kms capabable systems, we will need
some other way to access the backlight.

The approach taken in this patch moves most of the heavy lifting to a
helper that runs with root privileges and pipes our requested brightness
into the sysfs backlight interface. Where required, we use pkexec to
launch the helper with the elevated privilege.

v2: Amalgamate much more of the duplicate code.
    Keep the daemon and pipe alive for the lifetime of the backlight interface.
    Provide an alternative for systems without PolicyKit.

Signed-off-by: Hans de Goede <hdegoede@redhat.com> [v1]
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

1 files changed, 46 insertions, 0 deletions

diff --git a/src/backlight.h b/src/backlight.h
new file mode 100644
index 00000000..deecbd00
--- /dev/null
+++ b/src/backlight.h
@@ -0,0 +1,46 @@
+/***************************************************************************
+
+ Copyright 2014 Intel Corporation.  All Rights Reserved.
+
+ Permission is hereby granted, free of charge, to any person obtaining a
+ copy of this software and associated documentation files (the
+ "Software"), to deal in the Software without restriction, including
+ without limitation the rights to use, copy, modify, merge, publish,
+ distribute, sub license, and/or sell copies of the Software, and to
+ permit persons to whom the Software is furnished to do so, subject to
+ the following conditions:
+
+ The above copyright notice and this permission notice (including the
+ next paragraph) shall be included in all copies or substantial portions
+ of the Software.
+
+ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
+ IN NO EVENT SHALL INTEL, AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
+ DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+ OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR
+ THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+ **************************************************************************/
+
+#ifndef BACKLIGHT_H
+#define BACKLIGHT_H
+
+struct backlight {
+	char *iface;
+	int max;
+	int pid, fd;
+};
+
+#define BACKLIGHT_CLASS "/sys/class/backlight"
+
+int backlight_exists(const char *iface);
+
+int backlight_open(struct backlight *backlight, char *iface);
+int backlight_set(struct backlight *backlight, int level);
+int backlight_get(struct backlight *backlight);
+void backlight_disable(struct backlight *backlight);
+void backlight_close(struct backlight *backlight);
+
+#endif /* BACKLIGHT_H */