Add a switch to signal dock events to userspace.

Signed-off-by: Matthew Garrett <redacted>

---

I've done this as an input event rather than anything else since there 
isn't necessarily a terribly coherent concept of a dock device. HPs (for 
example) don't use ACPI for docking - the dock is simply an extension of 
devices that are already on the system. We can't sensibly create a dock 
platform device and then generate uevents on it. Doing it this way lets 
us standardise on a way to send docking events to userspace, which lets 
desktops do things like automatically expand onto external monitors when 
the system is docked.

diff --git a/include/linux/input.h b/include/linux/input.h
index 28a094f..0bc55ee 100644
--- a/include/linux/input.h
+++ b/include/linux/input.h

@@ -638,6 +638,7 @@ struct input_absinfo {
 #define SW_TABLET_MODE		0x01  /* set = tablet mode */
 #define SW_HEADPHONE_INSERT	0x02  /* set = inserted */
 #define SW_RADIO		0x03  /* set = radio enabled */
+#define SW_DOCK			0x04  /* set = plugged into dock */
 #define SW_MAX			0x0f
 #define SW_CNT			(SW_MAX+1)