backlight: update backlight status when necessary

We don't have to update a backlight status every time a blanking or
unblanking event comes because the backlight status may have already
been what we want.  Another thought is that one backlight device may be
shared by multiple framebuffers.  We don't hope blanking one of the
framebuffers may turn the backlight off for all the other framebuffers,
since they are likely being active to display something.

This patch makes the backlight status be updated only when the relevant
backlight device's use count changes from zero to one or from one to
zero.

Signed-off-by: Liu Ying <[email protected]>
Cc: Jingoo Han <[email protected]>
Cc: Jean-Christophe PLAGNIOL-VILLARD <[email protected]>
Cc: Tomi Valkeinen <[email protected]>
Cc: Jani Nikula <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

0 files changed, 0 insertions, 0 deletions