HID: add framebuffer support to PicoLCD device
Add framebuffer support to PicoLCD device with use of deferred-io.
Only changed areas of framebuffer get sent to device in order to
save USB bandwidth and especially resources on PicoLCD device or
allow higher refresh rate for a small area. Changed tiles are
determined while updating shadow framebuffer.
Signed-off-by: Bruno Prémont <bonbons@linux-vserver.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/Documentation/ABI/testing/sysfs-driver-hid-picolcd b/Documentation/ABI/testing/sysfs-driver-hid-picolcd
index 6fb4f21..14f52d7 100644
--- a/Documentation/ABI/testing/sysfs-driver-hid-picolcd
+++ b/Documentation/ABI/testing/sysfs-driver-hid-picolcd
@@ -15,3 +15,20 @@
disconnected and reconnects after above delay (default value
is 5 seconds though this default should not be relied on).
+
+What: /sys/bus/usb/devices/<busnum>-<devnum>:<config num>.<interface num>/<hid-bus>:<vendor-id>:<product-id>.<num>/fb_update_rate
+Date: March 2010
+Contact: Bruno Prémont <bonbons@linux-vserver.org>
+Description: Make it possible to adjust defio refresh rate.
+
+ Reading: returns list of available refresh rates (expressed in Hz),
+ the active refresh rate being enclosed in brackets ('[' and ']')
+
+ Writing: accepts new refresh rate expressed in integer Hz
+ within permitted rates.
+
+ Note: As device can barely do 2 complete refreshes a second
+ it only makes sense to adjust this value if only one or two
+ tiles get changed and it's not appropriate to expect the application
+ to flush it's tiny changes explicitely at higher than default rate.
+