drm/omapdrm: Implement fbdev emulation as in-kernel client

Move code from ad-hoc fbdev callbacks into DRM client functions
and remove the old callbacks. The functions instruct the client
to poll for changed output or restore the display. The DRM core
calls both, the old callbacks and the new client helpers, from
the same places. The new functions perform the same operation as
before, so there's no change in functionality.

Replace all code that initializes or releases fbdev emulation
throughout the driver. Instead initialize the fbdev client by a
single call to omapdrm_fbdev_setup() after omapdrm has registered
its DRM device. As in most drivers, omapdrm's fbdev emulation now
acts like a regular DRM client.

The fbdev client setup consists of the initial preparation and the
hot-plugging of the display. The latter creates the fbdev device
and sets up the fbdev framebuffer. The setup performs display
hot-plugging once. If no display can be detected, DRM probe helpers
re-run the detection on each hotplug event.

A call to drm_dev_unregister() releases the client automatically.
No further action is required within omapdrm. If the fbdev
framebuffer has been fully set up, struct fb_ops.fb_destroy
implements the release. For partially initialized emulation, the
fbdev client reverts the initial setup.

v2:
* init drm_client in this patch (Tomi)
* don't handle non-atomic modesetting (Tomi)

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230403104035.15288-6-tzimmermann@suse.de

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 234

Based on 1 normalized pattern(s):

this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license version 2 as
published by the free software foundation this program is
distributed in the hope that it will be useful but without any
warranty without even the implied warranty of merchantability or
fitness for a particular purpose see the gnu general public license
for more details you should have received a copy of the gnu general
public license along with this program if not see http www gnu org
licenses

extracted by the scancode license scanner the SPDX license identifier

GPL-2.0-only

has been chosen to replace the boilerplate/reference in 503 file(s).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexios Zavras <alexios.zavras@intel.com>
Reviewed-by: Allison Randal <allison@lohutok.net>
Reviewed-by: Enrico Weigelt <info@metux.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190602204653.811534538@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drm/omap: cleanup fbdev init/free

omap_fbdev_init() and omap_fbdev_free() use priv->fbdev directly.
However, omap_fbdev_init() returns the fbdev, and omap_drv.c also
assigns the return value to priv->fbdev. This is slightly confusing.

Clean this up by removing the omap_fbdev_init() return value, as we
don't care whether fbdev init succeeded or not. Also change omap_drv.c
to call omap_fbdev_free() always, and omap_fbdev_free() does the check
if fbdev was initialized.

While at it, rename omap_fbdev_free() to omap_fbdev_fini() to better
match the "init" counterpart.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

drm: omapdrm: Deconstruct the omap_drv.h header.

The number of function declarations in the omap_drv.h degrades
readability. To fix it, create new header files for each part of the
driver and move the related functions.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>