FBDEV

Framebuffer device

社區參與度不高，基本轉移到了DRM。

DRM/KMS

Direct Rendering Manager / KernelMode Setting

主流的圖形顯示方法，社區參與度高，支持圖形系統精細化操作，基本形成了一套圖顯系統開發的生態標準。

V4L2

Video For Linux 2

主要用于視頻捕獲的應用場景，并且需要特定輸出設備，對復雜圖顯控制器的支持不佳

##顯存Framebuffer

申請的一塊用于存儲顯示數據的內存區域，主要包括：
1）內存區域大小范圍
2）內存中待顯示數據的幀格式
3）內存中有效的區域，該部分是待顯示數據

其實現方法主要有3種：
1）基于CMA的
drivers/gpu/drm/drm_fb_cma_helper.c
2）基于Scatter Gather
drivers/gpu/drm/tegra/
3）基于IOMMU
drivers/gpu/drm/exynos/exynos_drm_iommu.c

顯存區域定義

幀格式定義

1/*24bppRGB*/
2#defineDRM_FORMAT_RGB888fourcc_code('R','G','2','4')
3#defineDRM_FORMAT_BGR888fourcc_code('B','G','2','4')
4
5/*32bppRGB*/
6#defineDRM_FORMAT_XRGB8888fourcc_code('X','R','2','4')
7#defineDRM_FORMAT_XBGR8888fourcc_code('X','B','2','4')
8#defineDRM_FORMAT_RGBX8888fourcc_code('R','X','2','4')
9#defineDRM_FORMAT_BGRX8888fourcc_code('B','X','2','4')

創建FRAME BUFFER

##CRTC

CRTC funcs

 1staticconststructdrm_crtc_funcsade_crtc_funcs={
 2.destroy=drm_crtc_cleanup,
 3.set_config=drm_atomic_helper_set_config,
 4.page_flip=drm_atomic_helper_page_flip,
 5.reset=drm_atomic_helper_crtc_reset,
 6    .atomic_duplicate_state=drm_atomic_helper_crtc_duplicate_state,
 7.atomic_destroy_state=drm_atomic_helper_crtc_destroy_state,
 8.enable_vblank=ade_crtc_enable_vblank,
 9.disable_vblank=ade_crtc_disable_vblank,
10};

CRTC helper funcs

1staticconststructdrm_crtc_helper_funcsade_crtc_helper_funcs={
2.mode_fixup=ade_crtc_mode_fixup,
3.mode_set_nofb=ade_crtc_mode_set_nofb,
4.atomic_begin=ade_crtc_atomic_begin,
5.atomic_flush=ade_crtc_atomic_flush,
6.atomic_enable=ade_crtc_atomic_enable,
7.atomic_disable=ade_crtc_atomic_disable,
8};

##PLANE

PLANE funcs

1staticstructdrm_plane_funcsade_plane_funcs={
2.update_plane=drm_atomic_helper_update_plane,
3.disable_plane=drm_atomic_helper_disable_plane,
4.destroy=drm_plane_cleanup,
5.reset=drm_atomic_helper_plane_reset,
6.atomic_duplicate_state=drm_atomic_helper_plane_duplicate_state,
7.atomic_destroy_state=drm_atomic_helper_plane_destroy_state,
8};

PLANE helper funcs

1staticconststructdrm_plane_helper_funcsade_plane_helper_funcs={
2.atomic_check=ade_plane_atomic_check,
3.atomic_update=ade_plane_atomic_update,
4.atomic_disable=ade_plane_atomic_disable,
5};

##ENCODER/CONNECTOR

ENCODER/helper funcs

 1staticconststructdrm_encoder_helper_funcsdw_encoder_helper_funcs={
 2.atomic_check=dsi_encoder_atomic_check,
 3.mode_valid=dsi_encoder_mode_valid,
 4.mode_set=dsi_encoder_mode_set,
 5.enable=dsi_encoder_enable,
 6.disable=dsi_encoder_disable
 7};
 8
 9staticconststructdrm_encoder_funcsdw_encoder_funcs={
10.destroy=drm_encoder_cleanup,
11};

CONNECTOR/helper funcs

 1staticconststructdrm_connector_helper_funcs
 2panel_bridge_connector_helper_funcs={
 3.get_modes=panel_bridge_connector_get_modes,
 4};
 5
 6staticconststructdrm_connector_funcspanel_bridge_connector_funcs={
 7.reset=drm_atomic_helper_connector_reset,
 8.fill_modes=drm_helper_probe_single_connector_modes,
 9.destroy=drm_connector_cleanup,
10.atomic_duplicate_state=drm_atomic_helper_connector_duplicate_state,
11.atomic_destroy_state=drm_atomic_helper_connector_destroy_state,
12};

##ioctl注冊

master是設備樹中的“超級設備（superdevice）”，負責管理該超級設備下的普通設備。component是由master管理的普通設備，要先初始化。

#初始化分為兩部分

component即普通設備，執行probe使用component_add函數注冊自己到component框架中。

##Master初始化

 1staticintkirin_drm_platform_probe(structplatform_device*pdev)
 2{
 3structdevice*dev=&pdev->dev;
 4structdevice_node*np=dev->of_node;
 5structcomponent_match*match=NULL;
 6structdevice_node*remote;
 7
 8remote=of_graph_get_remote_node(np,0,0);
 9if(!remote)
10return-ENODEV;
11
12drm_of_component_match_add(dev,&match,compare_of,remote);
13of_node_put(remote);
14
15returncomponent_master_add_with_match(dev,&kirin_drm_ops,match);
16}

##Component初始化

 1staticintdsi_probe(structplatform_device*pdev)
 2{
 3structdsi_data*data;
 4structdw_dsi*dsi;
 5structdsi_hw_ctx*ctx;
 6intret;
 7
 8data=devm_kzalloc(&pdev->dev,sizeof(*data),GFP_KERNEL);
 9if(!data){
10DRM_ERROR("failedtoallocatedsidata.
");
11return-ENOMEM;
12}
13dsi=&data->dsi;
14ctx=&data->ctx;
15dsi->ctx=ctx;
16
17ret=dsi_parse_dt(pdev,dsi);
18if(ret)
19returnret;
20
21platform_set_drvdata(pdev,data);
22
23returncomponent_add(&pdev->dev,&dsi_ops);
24}

##設備樹定義

 1ade:ade@f4100000{
 2compatible="hisilicon,hi6220-ade";
 3reg=<0x00xf41000000x00x7800>;
 4reg-names="ade_base";
 5hisilicon,noc-syscon=<&medianoc_ade>;
 6resets=<&media_ctrl?MEDIA_ADE>;
 7interrupts=<01154>;/*ldiinterrupt*/
 8
 9clocks=<&media_ctrl?HI6220_ADE_CORE>,
10<&media_ctrl?HI6220_CODEC_JPEG>,
11<&media_ctrl?HI6220_ADE_PIX_SRC>;
12/*clockname*/
13clock-names="clk_ade_core",
14"clk_codec_jpeg",
15"clk_ade_pix";
16
17assigned-clocks=<&media_ctrl?HI6220_ADE_CORE>,
18<&media_ctrl?HI6220_CODEC_JPEG>;
19assigned-clock-rates=<360000000>,<288000000>;
20dma-coherent;
21status="disabled";
22
23port{
24ade_out:endpoint{
25remote-endpoint=<&dsi_in>;
26};
27};
28};
29
30dsi:dsi@f4107800{
31compatible="hisilicon,hi6220-dsi";
32reg=<0x00xf41078000x00x100>;
33clocks=<&media_ctrl??HI6220_DSI_PCLK>;
34clock-names="pclk";
35status="disabled";
36
37ports{
38#address-cells=<1>;
39#size-cells=<0>;
40
41/*0forinputport*/
42port@0{
43reg=<0>;
44dsi_in:endpoint{
45remote-endpoint=<&ade_out>;
46};
47};
48};
49};

編輯：jq