GPU/DRM驱动

The Direct Rendering Manager (DRM) is a subsystem of the Linux kernel responsible for  
interfacing with GPUs of modern video cards. DRM exposes an API that user space programs  
can use to send commands and data to the GPU, and perform operations such as configuring  
the mode setting of the display. DRM was first developed as the kernel space component of  
the X Server's Direct Rendering Infrastructure,[1] but since then it has been used by other  
graphic stack alternatives such as Wayland. 

root@bf756b445919:~/linux/drivers/gpu/drm/sun4i# ls *.c
sun4i_backend.c  sun4i_dotclock.c  sun4i_framebuffer.c   sun4i_hdmi_enc.c       sun4i_layer.c  sun4i_tcon.c  sun6i_drc.c    sun8i_mixer.c
sun4i_crtc.c     sun4i_drv.c       sun4i_hdmi_ddc_clk.c  sun4i_hdmi_tmds_clk.c  sun4i_rgb.c    sun4i_tv.c    sun8i_layer.c

#include "sun5i-a13.dtsi"
#include "sun5i-reference-design-tablet.dtsi"

/ {
        model = "Q8 A13 Tablet";
        compatible = "allwinner,q8-a13", "allwinner,sun5i-a13";

        panel: panel {
                compatible = "urt,umsh-8596md-t", "simple-panel";
                #address-cells = <1>;
                #size-cells = <0>;

                port@0 {
                        reg = <0>;
                        /* TODO: lcd panel uses axp gpio0 as enable pin */
                        backlight = <&backlight>;
                        #address-cells = <1>;
                        #size-cells = <0>;

                        panel_input: endpoint@0 {
                                reg = <0>;
                                remote-endpoint = <&tcon0_out_lcd>;
                        };
                };
        };
};

&be0 {
        status = "okay";
};

&tcon0 {
        pinctrl-names = "default";
        pinctrl-0 = <&lcd_rgb666_pins>;
        status = "okay";
};

&tcon0_out {
        tcon0_out_lcd: endpoint@0 {
                reg = <0>;
                remote-endpoint = <&panel_input>;
        };
};