video: of_display_timing.h: include errno.h

If CONFIG_OF is not enabled, default of_get_display_timing() returns an
errno, so include the header.

Fixes: 422b67e0b31a ("videomode: provide dummy inline functions for !CONFIG_OF")
Suggested-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Helge Deller <deller@gmx.de>

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 428

Based on 1 normalized pattern(s):

this file is released under the gplv2

extracted by the scancode license scanner the SPDX license identifier

GPL-2.0-only

has been chosen to replace the boilerplate/reference in 68 file(s).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Armijn Hemel <armijn@tjaldur.nl>
Reviewed-by: Allison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190531190114.292346262@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

video: of: display_timing: Remove of_display_timings_exist() function

Since introduction of of_display_timings_exist() function in commit
cc3f414cf2e40 ("video: add of helper for display timings/videomode") it
didn't attract any users, and the function has no potential, because
of_get_display_timings() covers its functionality and does more.

Drop the unused exported function from the kernel.

Signed-off-by: Vladimir Zapolskiy <vz@mleia.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>

video: of: Constify node argument to display timing functions

The node pointer passed to the display timing functions is never
modified, make it const.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ti.com>

videomode: provide dummy inline functions for !CONFIG_OF

If CONFIG_OF is disabled but we build any driver that tries to
use of_get_display_timing, we get this link error:

ERROR: "of_get_display_timing" [drivers/gpu/drm/rcar-du/rcar-du-drm.ko] undefined!

This adds an empty inline function as an alternative, to avoid changing
each driver using this function when we want to build them without
CONFIG_OF.

Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>

video: of_display_timing.h: Declare 'display_timing'

Commit ffa3fd21de ("videomode: implement public of_get_display_timing()") causes
the following build warning:

include/video/of_display_timing.h:18:10: warning: 'struct display_timing' declared inside parameter list [enabled by default]
include/video/of_display_timing.h:18:10: warning: its scope is only this definition or declaration, which is probably not what you want [enabled by default]

Declare 'display_timing' to avoid the build warning.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>

videomode: implement public of_get_display_timing()

The current of_get_display_timings() reads multiple display timings,
allocating memory for the entries. However, most of the time when
parsing display timings from DT data is needed, there's only one display
timing as it's not common for a LCD panel to support multiple videomodes.

This patch creates a new function:

int of_get_display_timing(struct device_node *np, const char *name,
struct display_timing *dt);

which can be used to parse a single display timing entry from the given
node name.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: Steffen Trumtrar <s.trumtrar@pengutronix.de>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Philipp Zabel <p.zabel@pengutronix.de>

video: add of helper for display timings/videomode

This adds support for reading display timings from DT into a struct
display_timings. The of_display_timing implementation supports multiple
subnodes. All children are read into an array, that can be queried.

If no native mode is specified, the first subnode will be used.

For cases where the graphics driver knows there can be only one
mode description or where the driver only supports one mode, a helper
function of_get_videomode is added, that gets a struct videomode from DT.

Signed-off-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Acked-by: Stephen Warren <swarren@nvidia.com>
Reviewed-by: Thierry Reding <thierry.reding@avionic-design.de>
Acked-by: Thierry Reding <thierry.reding@avionic-design.de>
Tested-by: Thierry Reding <thierry.reding@avionic-design.de>
Tested-by: Philipp Zabel <p.zabel@pengutronix.de>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Tested-by: Afzal Mohammed <Afzal@ti.com>
Tested-by: Rob Clark <robclark@gmail.com>
Tested-by: Leela Krishna Amudala <leelakrishna.a@gmail.com>