The original version duplicated more or less the same algorithms for
both system and i/o memory.

In this version the drawing algorithms (copy/fill/blit) are separate
from the memory access (system and i/o). The two parts are getting
combined in the loadable module sources. This also makes it more robust
against wrong memory access type or alignment mistakes as there's no
direct pointer access or arithmetic in the algorithm sources anymore.

Due to liberal use of inlining the compiled result is a single function
in all 6 cases, without unnecessary function calls. Unlike earlier the
use of macros could be minimized as apparently both gcc and clang is
capable now to do the same with inline functions just as well.

What wasn't quite the same in the two variants is the support for pixel
order reversing. This version is capable to do that for both system and
I/O memory, and not only for the latter. As demand for low bits per
pixel modes isn't high there's a configuration option to enable this
separately for the CFB and SYS modules.

The pixel reversing algorithm is different than earlier and was designed
so that it can take advantage of bit order reversing instructions on
architectures which have them. And even for higher bits per pixel modes
like four bpp.

One of the shortcomings of the earlier version was the incomplete
support for foreign endian framebuffers. Now all three drawing
algorithms produce correct output on both endians with native and
foreign framebuffers. This is one of the important differences even if
otherwise the algorithms don't look too different than before.

All three routines work now with aligned native word accesses. As a
consequence blitting isn't limited to 32 bits on 64 bit architectures as
it was before.

The old routines silently assumed that rows are a multiple of the word
size. Due to how the new routines function this isn't a requirement any
more and access will be done aligned regardless. However if the
framebuffer is configured like that then some of the fast paths won't be
available.

As this code is supposed to be running on all supported architectures it
wasn't optimized for a particular one. That doesn't mean I haven't
looked at the disassembly. That's where I noticed that it isn't a good
idea to use the fallback bitreversing code for example.

The low bits per pixel modes should be faster than before as the new
routines can blit 4 pixels at a time.

On the higher bits per pixel modes I retained the specialized aligned
routines so it should be more or less the same, except on 64 bit
architectures. There the blitting word size is double now which means 32
BPP isn't done a single pixel a time now.

The code was tested on x86, amd64, mips32 and mips64. The latter two in
big endian configuration. Originally thought I can get away with the
first two, but with such bit twisting code byte ordering is tricky and
not really possible to get right without actually verifying it.

While writing such routines isn't rocket science a lot of time was spent
on making sure that pixel ordering, foreign byte order, various bits per
pixels, cpu endianness and word size will give the expected result in
all sorts of combinations without making it overly complicated or full
with special cases.

Signed-off-by: Zsolt Kajtar <soci@c64.rulez.org>
Signed-off-by: Helge Deller <deller@gmx.de>

Do not select BACKLIGHT_CLASS_DEVICE from FB_BACKLIGHT. The latter
only controls backlight support within fbdev core code and data
structures.

Make fbdev drivers depend on BACKLIGHT_CLASS_DEVICE and let users
select it explicitly. Fixes warnings about recursive dependencies,
such as

error: recursive dependency detected!
	symbol BACKLIGHT_CLASS_DEVICE is selected by FB_BACKLIGHT
	symbol FB_BACKLIGHT is selected by FB_SH_MOBILE_LCDC
	symbol FB_SH_MOBILE_LCDC depends on FB_DEVICE
	symbol FB_DEVICE depends on FB_CORE
	symbol FB_CORE is selected by DRM_GEM_DMA_HELPER
	symbol DRM_GEM_DMA_HELPER is selected by DRM_PANEL_ILITEK_ILI9341
	symbol DRM_PANEL_ILITEK_ILI9341 depends on BACKLIGHT_CLASS_DEVICE

BACKLIGHT_CLASS_DEVICE is user-selectable, so making drivers adapt to
it is the correct approach in any case. For most drivers, backlight
support is also configurable separately.

v3:
- Select BACKLIGHT_CLASS_DEVICE in PowerMac defconfigs (Christophe)
- Fix PMAC_BACKLIGHT module dependency corner cases (Christophe)
v2:
- s/BACKLIGHT_DEVICE_CLASS/BACKLIGHT_CLASS_DEVICE (Helge)
- Fix fbdev driver-dependency corner case (Arnd)

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20241216074450.8590-2-tzimmermann@suse.de

Commit 95da53d63dcf ("drm/omapdrm: Use regular fbdev I/O helpers")
stopped console from updating for command mode displays because there is
no damage handling in fb_sys_write() unlike we had earlier in
drm_fb_helper_sys_write().

Let's fix the issue by adding FB_GEN_DEFAULT_DEFERRED_DMAMEM_OPS and
FB_DMAMEM_HELPERS_DEFERRED as suggested by Thomas. We cannot use the
FB_DEFAULT_DEFERRED_OPS as fb_deferred_io_mmap() won't work properly
for write-combine.

Fixes: 95da53d63dcf ("drm/omapdrm: Use regular fbdev I/O helpers")
Suggested-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240228063540.4444-3-tony@atomide.com

Add CONFIG_VIDEO for common code in drivers/video/. Use the option to
select helpers for the video= parameter. Replaces CONFIG_VIDEO_CMDLINE.

Other common code in drivers/video/ can be moved behind CONFIG_VIDEO,
which will simplify the Kconfig rules.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20240118090721.7995-2-tzimmermann@suse.de

Drop the default implementations for file read, write and mmap
operations. Each fbdev driver must now provide an implementation
and select any necessary helpers. If no implementation has been
set, fbdev returns an errno code to user space. The code is the
same as if the operation had not been set in the file_operations
struct.

This change makes the fbdev helpers for I/O memory optional. Most
systems only use system-memory framebuffers via DRM's fbdev emulation.

v2:
	* warn once if I/O callbacks are missing (Javier)

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231127131655.4020-33-tzimmermann@suse.de

Rename the token to harmonize naming among various helpers. For
example, I/O-memory helpers use FB_IOMEM_FOPS.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231127131655.4020-28-tzimmermann@suse.de

drm-misc-next for v6.7-rc1:

drm-misc-next-2023-10-19 + following:

UAPI Changes:

Cross-subsystem Changes:
- Convert fbdev drivers to use fbdev i/o mem helpers.

Core Changes:
- Use cross-references for macros in docs.
- Make drm_client_buffer_addb use addfb2.
- Add NV20 and NV30 YUV formats.
- Documentation updates for create_dumb ioctl.
- CI fixes.
- Allow variable number of run-queues in scheduler.

Driver Changes:
- Rename drm/ast constants.
- Make ili9882t its own driver.
- Assorted fixes in ivpu, vc4, bridge/synopsis, amdgpu.
- Add planar formats to rockchip.

Signed-off-by: Dave Airlie <airlied@redhat.com>
From: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/3d92fae8-9b1b-4165-9ca8-5fda11ee146b@linux.intel.com

This is needed to add the msm pr which is based on a higher base.

Signed-off-by: Dave Airlie <airlied@redhat.com>

Provide helpers for accessing I/O memory in a helper module. The fbdev
core uses these helpers, so select the module unconditionally for fbdev.
Drivers will later be able to select the module individually and the
helpers will become optional.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230927074722.6197-2-tzimmermann@suse.de

As a result of the recent Kconfig reworks, the default settings for the
framebuffer interfaces changed in unexpected ways:

Configurations that leave CONFIG_FB disabled but use DRM now get
DRM_FBDEV_EMULATION by default. This also turns on the deprecated /dev/fb
device nodes for machines that don't actually want it.

In turn, configurations that previously had DRM_FBDEV_EMULATION enabled
now only get the /dev/fb front-end but not the more useful framebuffer
console, which is not selected any more.

We had previously decided that any combination of the three frontends
(FB_DEVICE, FRAMEBUFFER_CONSOLE and LOGO) should be selectable, but the
new default settings mean that a lot of defconfig files would have to
get adapted.

Change the defaults back to what they were in Linux 6.5:

 - Leave DRM_FBDEV_EMULATION turned off unless CONFIG_FB
   is enabled. Previously this was a hard dependency but now the two are
   independent. However, configurations that enable CONFIG_FB probably
   also want to keep the emulation for DRM, while those without FB
   presumably did that intentionally in the past.

 - Leave FB_DEVICE turned off for FB=n. Following the same
   logic, the deprecated option should not automatically get enabled
   here, most users that had FB turned off in the past do not want it,
   even if they want the console

 - Turn the FRAMEBUFFER_CONSOLE option on if
   DRM_FBDEV_EMULATION is set to avoid having to change defconfig
   files that relied on it being selected unconditionally in the past.
   This also makes sense since both LOGO and FB_DEVICE are now disabled
   by default for builds without CONFIG_FB, but DRM_FBDEV_EMULATION
   would make no sense if all three are disabled.

Fixes: a5ae331edb02b ("drm: Drop select FRAMEBUFFER_CONSOLE for DRM_FBDEV_EMULATION")
Fixes: 701d2054fa317 ("fbdev: Make support for userspace interfaces configurable")
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230911205338.2385278-1-arnd@kernel.org