Products built on the same board often differ only in branding. On UEFI systems the firmware hands the operating system its boot logo through the ACPI BGRT; a device tree system has no such table, so today the logo is built into the kernel, and each product needs its own kernel image. With U-Boot's Falcon mode the device tree is the only thing that reaches the kernel, so it is also the only place the logo can come from.
Add a "boot-logo" node under /chosen. The node lives there because a logo is configuration handed over by firmware rather than a description of the hardware, as simple-framebuffer nodes already are. The image is a BMP with 24 bits per pixel and no compression, the format of the BGRT image, so that one file serves the firmware splash, a BMP loaded as firmware and this node alike. It is carried either in an "image" property, which dtc fills in from the file with /incbin/, or in a reserved memory region the bootloader loaded it into, named by "memory-region". Exactly one of the two must be present. "logo-position" takes -1 on an axis to mean centre on that axis, which is the only way to say it when the device tree does not know the image size, and "logo-offset" is added afterwards. "rotation" counts degrees counter clockwise, as for panels, and turns the image rather than the screen, so position and offset stay in screen pixels. The optional "background-color" goes with the image, since a logo designed for one background looks wrong on another. Assisted-by: Claude:claude-opus-5-5 Signed-off-by: Màxim Pedraza Padilla <[email protected]> --- .../bindings/display/boot-logo.yaml | 151 ++++++++++++++++++ MAINTAINERS | 1 + 2 files changed, 152 insertions(+) create mode 100644 Documentation/devicetree/bindings/display/boot-logo.yaml diff --git a/Documentation/devicetree/bindings/display/boot-logo.yaml b/Documentation/devicetree/bindings/display/boot-logo.yaml new file mode 100644 index 000000000000..b540a04deb78 --- /dev/null +++ b/Documentation/devicetree/bindings/display/boot-logo.yaml @@ -0,0 +1,151 @@ +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) +%YAML 1.2 +--- +$id: http://devicetree.org/schemas/display/boot-logo.yaml# +$schema: http://devicetree.org/meta-schemas/core.yaml# + +title: Boot logo supplied by the device tree + +maintainers: + - Francesco Valla <[email protected]> + - Màxim Pedraza Padilla <[email protected]> + +description: | + An image for the operating system to show on the display while it boots, + handed over by the firmware together with where and how to show it. + + Products built on the same board often differ only in branding. Carrying + the logo in the device tree lets a single kernel image serve all of them, + each booting with its own device tree, and it works where the device tree + is the only thing that reaches the kernel, as with U-Boot's Falcon mode. + It plays the part the ACPI BGRT plays on UEFI systems. + + Since a logo is configuration rather than a description of the hardware, + the node lives under /chosen, next to the other things firmware hands to + the operating system. + + The image is a BMP file with a 40 byte BITMAPINFOHEADER, 24 bits per pixel + and no compression, the format of the BGRT image. It is carried either in + the node itself or in a reserved memory region the bootloader loaded it + into, never both. + +properties: + $nodename: + const: logo + + compatible: + const: boot-logo + + image: + $ref: /schemas/types.yaml#/definitions/uint8-array + description: + The BMP file itself, byte for byte, which dtc can fill in from the file + with /incbin/. The device tree stays in memory for as long as the + system runs, so this is meant for small images; larger ones belong in + a reserved memory region. + + memory-region: + maxItems: 1 + description: | + Reserved memory region the bootloader loaded the BMP file into, starting + at the beginning of the region. The BMP header says how much of the + region is image. + + This keeps the image out of the device tree, so that it can be changed + without rebuilding the device tree, for instance by loading it from a + partition of its own that userspace can update. + + Memory keeps its contents across a reset, and may even across a short + power cycle, so a bootloader that loads no image into the region has to + clear it: the operating system cannot tell a stale image from a fresh + one. + + logo-position: + $ref: /schemas/types.yaml#/definitions/int32-array + description: + X and Y coordinates, in screen pixels, of the top left corner of the + image once it has been rotated. A value of -1 on an axis centres the + image on that axis instead, which is the only way to say it when the + device tree does not know the image size, as with a memory region. + Defaults to centring on both axes. + items: + - description: X coordinate, or -1 to centre horizontally + minimum: -1 + maximum: 65535 + - description: Y coordinate, or -1 to centre vertically + minimum: -1 + maximum: 65535 + + logo-offset: + $ref: /schemas/types.yaml#/definitions/int32-array + description: + X and Y displacement, in screen pixels, applied after the image has been + placed. Mostly useful together with a centred axis, to land the image + somewhere other than the middle of a panel whose visible area is not + the middle of the mode. + items: + - description: X displacement + minimum: -65535 + maximum: 65535 + - description: Y displacement + minimum: -65535 + maximum: 65535 + + rotation: + $ref: /schemas/types.yaml#/definitions/uint32 + description: + Rotation applied to the image before it is shown, in degrees counter + clockwise, as for the rotation property of panels. It turns the image + and not the screen, so a quarter turn swaps how much room the image + takes up, but logo-position and logo-offset stay in screen pixels + either way. + enum: [0, 90, 180, 270] + default: 0 + + background-color: + $ref: /schemas/types.yaml#/definitions/uint32 + description: + Colour of the rest of the screen, as 0xRRGGBB. When absent, the + operating system uses its own default. + maximum: 0xffffff + +required: + - compatible + +# The image lives either in the node or in a reserved memory region, +# never both and never neither. +oneOf: + - required: + - image + - required: + - memory-region + +additionalProperties: false + +examples: + - | + // A 2x1 image, red and blue, centred and 120 pixels below the middle + / { + compatible = "foo"; + model = "foo"; + #address-cells = <1>; + #size-cells = <1>; + + chosen { + logo { + compatible = "boot-logo"; + /* Normally: image = /incbin/("logo.bmp"); */ + image = /bits/ 8 <0x42 0x4d 0x3e 0x00 0x00 0x00 0x00 0x00 + 0x00 0x00 0x36 0x00 0x00 0x00 0x28 0x00 + 0x00 0x00 0x02 0x00 0x00 0x00 0x01 0x00 + 0x00 0x00 0x01 0x00 0x18 0x00 0x00 0x00 + 0x00 0x00 0x08 0x00 0x00 0x00 0x13 0x0b + 0x00 0x00 0x13 0x0b 0x00 0x00 0x00 0x00 + 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 + 0xff 0xff 0x00 0x00 0x00 0x00>; + logo-position = <(-1) (-1)>; + logo-offset = <0 120>; + background-color = <0x1e1e28>; + }; + }; + }; diff --git a/MAINTAINERS b/MAINTAINERS index 44730414e5df..9f057fdb3bdb 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -9161,6 +9161,7 @@ M: Màxim Pedraza Padilla <[email protected]> L: [email protected] S: Maintained T: git https://gitlab.freedesktop.org/drm/misc/kernel.git +F: Documentation/devicetree/bindings/display/boot-logo.yaml F: drivers/gpu/drm/clients/drm_splash.c DRM TTM SUBSYSTEM -- 2.39.5
