drm/sysfb: Add efidrm for EFI displays

JIRA: https://issues.redhat.com/browse/RHEL-113577
Upstream Status: v6.16

Only the changes to "drivers/gpu/drm/sysfb/Kconfig" and
"include/video/pixel_format.h" are backported.
The changes for "drivers/gpu/drm/sysfb/efidrm.c" present in the
upstream patch are already available in this tree.

NOTE: This commit does not compile due to missing RHEL-specific fix-ups,
which are split out into separate Git commits following this one.

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commit 32ae90c
Author: Thomas Zimmermann <tzimmermann@suse.de>
Date:   Tue Apr 1 11:37:17 2025 +0200

    drm/sysfb: Add efidrm for EFI displays

    Add support for screen_info setups with VIDEO_TYPE_EFI. Provide the
    minimum functionality of reading modes, updating and clearing the display.

    There is existing support for these displays provided by simpledrm with
    CONFIG_SYSFB_SIMPLEFB=y. Using efidrm over simpledrm will allows for the
    mapping of video memory with correct caching. Simpledrm always assumes WC
    caching, while fully cached memory is possible with efidrm. Efidrm will
    also allow for the use of additional functionality provided by EFI, such
    as EDID information.

    In addition to efidrm, add struct pixel_format plus initializer macros.
    The type and macros describe pixel formats in a generic way on order to
    find the DRM format from the screen_info settings. Similar existing code
    in SIMPLEFB_FORMATS and fbdev is not really what is needed in efidrm,
    but SIMPLEFB_FORMATS can later be converted to struct pixel_format.

    v4:
    - depend on CONFIG_EFI
    - disallow module for now as efi_mem_desc_lookup() is not exported
    v3:
    - depend on !SYSFB_SIMPLEFB (Javier)

    Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
    Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
    Link: https://lore.kernel.org/r/20250401094056.32904-15-tzimmermann@suse.de

Signed-off-by: José Expósito <jexposit@redhat.com>

Author: jexposit

drivers/gpu/drm/sysfb/Kconfig

@@ -8,8 +8,8 @@ config DRM_SYSFB_HELPER
 	depends on DRM
 
 config DRM_EFIDRM
-	tristate "EFI framebuffer driver"
-	depends on DRM && MMU && EFI && (!SYSFB_SIMPLEFB || COMPILE_TEST)
+	bool "EFI framebuffer driver"
+	depends on (DRM=y) && MMU && EFI && (!SYSFB_SIMPLEFB || COMPILE_TEST)
 	select APERTURE_HELPERS
 	select DRM_CLIENT_SELECTION
 	select DRM_GEM_SHMEM_HELPER

include/video/pixel_format.h

@@ -0,0 +1,41 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef VIDEO_PIXEL_FORMAT_H
+#define VIDEO_PIXEL_FORMAT_H
+
+struct pixel_format {
+	unsigned char bits_per_pixel;
+	bool indexed;
+	union {
+		struct {
+			struct {
+				unsigned char offset;
+				unsigned char length;
+			} alpha, red, green, blue;
+		};
+		struct {
+			unsigned char offset;
+			unsigned char length;
+		} index;
+	};
+};
+
+#define PIXEL_FORMAT_XRGB1555 \
+	{ 16, false, { .alpha = {0, 0}, .red = {10, 5}, .green = {5, 5}, .blue = {0, 5} } }
+
+#define PIXEL_FORMAT_RGB565 \
+	{ 16, false, { .alpha = {0, 0}, .red = {11, 5}, .green = {5, 6}, .blue = {0, 5} } }
+
+#define PIXEL_FORMAT_RGB888 \
+	{ 24, false, { .alpha = {0, 0}, .red = {16, 8}, .green = {8, 8}, .blue = {0, 8} } }
+
+#define PIXEL_FORMAT_XRGB8888 \
+	{ 32, false, { .alpha = {0, 0}, .red = {16, 8}, .green = {8, 8}, .blue = {0, 8} } }
+
+#define PIXEL_FORMAT_XBGR8888 \
+	{ 32, false, { .alpha = {0, 0}, .red = {0, 8}, .green = {8, 8}, .blue = {16, 8} } }
+
+#define PIXEL_FORMAT_XRGB2101010 \
+	{ 32, false, { .alpha = {0, 0}, .red = {20, 10}, .green = {10, 10}, .blue = {0, 10} } }
+
+#endif