Simple framebuffer (simple-framebuffer)

<tt>simple-framebuffer</tt> platform driver

Implementation: **components/drivers/graphic/framebuffer/fb-simple.c**. Registers a **struct rt_graphic_device** from a fixed memory window described in device tree (Linux **simple-framebuffer** binding style).

Device tree (typical)

framebuffer@0 {
    compatible = "simple-framebuffer";
    reg = <0x0 0x00800000>;
    width = <1920>;
    height = <1080>;
    stride = <7680>;
    format = "a8r8g8b8";   /* see driver format table */
    clocks = <&disp_clk>;  /* optional, RT_USING_CLK */
    power-supplies = <&vdd>; /* optional, RT_USING_REGULATOR */
};

Probe flow

1. Parse **width**, **height**, **stride**, **format** → internal **simplefb_format** (bits per pixel, RT graphic mode).
2. **ioremap** (or use physical) **reg** → **screen_base**, compute **screen_size**.
3. Optional **rt_clk_array** prepare/enable; optional regulator **enable** array.
4. Fill **rt_graphic_device** ops (set_pixel, get_pixel, draw_hline, etc.) and **rt_device_register**.

Supported formats

Driver table maps string names (e.g. **r5g6b5**, **a8r8g8b8**, **x8r8g8b8**) to **rt_graphic_info** mode and bpp. Unknown **format** fails probe.

Remove

Disable clocks/regulators, unmap framebuffer memory, unregister graphic device.

Driver / BSP quick notes

Topic	Guidance
Cache	CPU-accessible framebuffer RAM must use correct MMU cache attributes; if cacheable, maintain with **rt_hw_cpu_dcache_ops** — see Hardware cache (hwcache)
Stride	Must match hardware line pitch (bytes), not always width * bpp/8
Primary display	Pair with Graphics (DM) / graphic_primary.c if multiple heads
No GPU	This is linear FB only—no command queue; use a SoC GPU driver if you need acceleration

See also

• Graphics (DM)
• components/drivers/graphic/framebuffer/fb-simple.c
• components/drivers/graphic/graphic.c