[PATCHv5][ 1/5] fbdev: Add the lacking FB_SYNC_* for matching the DISPLAY_FLAGS_*

On Fri, Jan 10, 2014 at 02:37:40PM +0200, Tomi Valkeinen wrote:

I don't think this is better than the previous version where
FB_SYNC_DE_HIGH_ACT and FB_SYNC_PIXDAT_HIGH_ACT were in
include/uapi/linux/fb.h. Now those flag defines are not visible to the
userspace, but the actual flags are still visible from the var->sync field.

It's true what Russell replied to the previous version, that the
userspace has no idea how to handle those new flags. But then again, for
LCDs, the userspace has no idea how to handle, say, hsync polarity either.

In any case, splitting the FB_SYNC_ defines into uapi and
kernel-internal header files, but still giving the kernel-internal
values to userspace is surely wrong.

The difference between the sync states and these other flags is that
the sync states are part of the mode definition - as per the CEA-861
documentation.

However, that does not extend to LCD panels, which generally need to
have one set of timings, with the various control signals at certain
polarities - and those control signal polarities are a property of
the panel itself, not of the displayed mode.  So, if you know that
you have LCD panel X, and it needs control signals with a certain
polarity, that is how you configure the hardware _irrespective_ of
what userspace says that the sync states should be.

The sync states specified by userspace should of course be used for
the sync pulses being sent to a VGA display or HDMI sink.

-- 
FTTC broadband for 0.8mile line: 5.8Mbps down 500kbps up.  Estimation
in database were 13.1 to 19Mbit for a good line, about 7.5+ for a bad.
Estimate before purchase was "up to 13.2Mbit".