Add support for the gskill-mx780

This commit adds complete (with the exception of LEDs and a few other
small things) support for configuring the G.Skill Ripjaws MX780. So far
this has been tested on firmware versions 19 and 21, and both of them
seem to work perfectly with this.

Changes since v1:
- Lots of style fixes
- Remove reset hook, comment out with #if 0 in case of usage in the
  future
- Add ret = -EAGAIN check in the loop in gskill_general_cmd()
- Explain why we wait longer then the spec says to in
  gskill_general_cmd()
- Check that buf[0] is set to GSKILL_GENERAL_CMD in gskill_general_cmd()
- Add some notes as to why we don't use gskill_general_cmd() in
  gskill_select_profile()
- Cleanup return codes, change gskill_general_cmd() so it only returns
  valid error codes. In places not using gskill_general_cmd(), do
    return rc < 0 ? rc : -EPROTO;
- Split command for selecting the macro to read/write from into it's own
  function, just like we do with the profile
- Move profile count workaround into it's own function, make explicit
  note of why it's needed
- Add proper support for reading/writing profile/macro names, ensure
  they aren't left blank so as to not confuse G.Skill's software
- Use HID kbd modifier codes for translating macro kbd modifier codes
- Use AS_MASK instead of (1 << foo) (apparently we already had this :)

Signed-off-by: Lyude <cpaul@redhat.com>

hwdb/70-libratbag-mouse.hwdb

@@ -187,3 +187,12 @@ mouse:usb:v046dpc539:name:*:
 mouse:usb:v1e7dp2e22:name:*:
  RATBAG_DRIVER=roccat
  RATBAG_SVG=roccat-kone-xtd.svg
+
+
+##########################################
+# G.Skill
+##########################################
+
+# MX-780
+mouse:usb:v28dap3101:name:*:
+ RATBAG_DRIVER=gskill

src/Makefile.am

@@ -12,6 +12,7 @@ libratbag_la_SOURCES =			\
 	driver-hidpp20.c		\
 	driver-hidpp10.c		\
 	driver-roccat.c			\
+	driver-gskill.c			\
 	driver-test.c			\
 	libratbag.c			\
 	libratbag.h			\

src/libratbag-private.h

@@ -418,6 +418,7 @@ struct ratbag_driver etekcity_driver;
 struct ratbag_driver hidpp20_driver;
 struct ratbag_driver hidpp10_driver;
 struct ratbag_driver roccat_driver;
+struct ratbag_driver gskill_driver;
 
 struct ratbag_device*
 ratbag_device_new(struct ratbag *ratbag, struct udev_device *udev_device,

src/libratbag.c

@@ -534,6 +534,7 @@ ratbag_create_context(const struct ratbag_interface *interface,
 	ratbag_register_driver(ratbag, &hidpp20_driver);
 	ratbag_register_driver(ratbag, &hidpp10_driver);
 	ratbag_register_driver(ratbag, &roccat_driver);
+	ratbag_register_driver(ratbag, &gskill_driver);
 
 	return ratbag;
 }