Wayland & Weston 显示服务启动log分析启动流程
前言
众所周知，i.MX系列芯片在多媒体领域有着广泛的应用。基于此点，我们在之前的系列中介绍了多种不同的显示接口及GStreamer管道的搭建方法。本文我们将分析说明显示部分的另一重要组成部分 -- Wayland & Weston。
执行步骤：
1 预定板子：
打开云实验室网页，点击右上角登陆按钮输入账号密码。
https://aiotcloud.nxp.com.cn/登陆后依次点击硬件 -> i.MX 9 系列开发板
找到i.MX 93 EVK “可立即使用”状态，并且外设中有DY1212-4856 LVDS屏幕的板子，如下图点击“i.MX93EVK #2”进入。
然后点击“立即预定“按钮：
选择立即使用，填写使用结束时间
然后进入我的预定，
点击右侧蓝色“调试”按钮，之后就进入到板子的实物页面和系统启动log页面。到此为止，板子预定并且启动成功。
默认用户名为“root”，默认密码为“root”
Wayland & Weston 的应用
在之前的文章中，手把手教你利用systemd设置开机自启动，我们介绍了systemd是一种用于 Linux 操作系统的初始化系统和服务管理器，负责启动和管理系统中各种服务和进程。Weston同样可以通过systemd的service在Kernel启动过程中进行自启动，我们可以通过systemctl list-unit-files --type=service 命令查看Weston所对应的service名称：
随后，可以找到其启动服务对应的文件路径为 /lib/systemd/system/weston.service。从中可以看到Weston启动的依赖项及启动顺序，其中Service部分定义了启动时所执行文件及log保存目录：
ExecStart=/usr/bin/weston --log=${XDG_RUNTIME_DIR}/weston.log --modules=systemd-notify.so通过Weston的启动log (/run/user/0/weston.log)，我们可以对Weston的启动进行进一步的分析，可以看到BSP及Weston所使用的的对应版本号。针对i.MX93, Lf 6.1.55 将搭配 11.0.0.3 版本Weston使用：
[09:49:27.620] weston 11.0.3
https://wayland.freedesktop.org
Bug reports to: https://gitlab.freedesktop.org/wayland/weston/issues/
Build: 11.0.3-54-gba6a8a02+
[09:49:27.621] Command line: /usr/bin/weston --log=/run/user/0/weston.log --modules=systemd-notify.so
[09:49:27.621] OS: Linux, 6.1.55+gde8d5a614f8f, #1 SMP PREEMPT Fri Mar 8 07:53:09 UTC 2024, aarch64随后，我们可以看到其调用了配置文件，weston.ini，进行显示相关配置。在之前的多篇演示示例中，我们便是通过设置weston.ini实现多屏同显及相应分辨率的设置。
[09:49:27.623] Using config file '/etc/xdg/weston/weston.ini'紧接着可以看到Weston默认使用DRM作为后端(backend)。该模式下，Wayland输出界面直接通过/dev/dri/card0节点来显示：
[09:49:27.631] Loading module '/usr/lib/libweston-11/drm-backend.so'
[09:49:27.637] initializing drm backend
[09:49:27.637] Trying logind launcher...
[09:49:27.650] logind: session control granted
[09:49:27.663] using /dev/dri/card0
[09:49:27.663] DRM: supports atomic modesetting
[09:49:27.663] DRM: does not support GBM modifiers
[09:49:27.663] DRM: supports picture aspect ratio我们使用i.MX93官方配套的DSI屏幕 (MX8-DSI-OLED1A)作为显示配置，其所配套的设备树为 'imx93-11x11-evk-rm67199.dtb'。从DTS中我们可以看到，这款DSI屏幕配置触屏，即Goodix：
&lpi2c1 {
touchscreen@14 {
compatible = "goodix,gt1151";
reg = <0x14>;
interrupt-parent = <&pcal6524>;
interrupts = <7 IRQ_TYPE_EDGE_FALLING>;
irq-gpios = <&pcal6524 7 GPIO_ACTIVE_HIGH>;
reset-gpios = <&adp5585gpio 9 GPIO_ACTIVE_HIGH>;
edge-failling-trigger;
touchscreen-size-x = <1080>;
touchscreen-size-y = <1920>;
};
};因此，我们可以在Weston的log中看到触控事件的注册。关于触控，键盘及鼠标在Weston中的输入设置，我们将在未来的理论篇中通过代码详细说明：
[09:49:27.804] event1 - Goodix Capacitive TouchScreen: is tagged by udev as: Keyboard Touchscreen
[09:49:27.805] event1 - Goodix Capacitive TouchScreen: device is a keyboard
[09:49:27.805] event1 - Goodix Capacitive TouchScreen: device is a touch device
[09:49:27.813] event2 - WM8962 Beep Generator: not tagged as supported input device
[09:49:27.813] event2 - not using input device '/dev/input/event2'
[09:49:27.822] event0 - 44440000.bbnsm:pwrkey: is tagged by udev as: Keyboard
[09:49:27.822] event0 - 44440000.bbnsm:pwrkey: device is a keyboard
[09:49:27.863] Touchscreen - Goodix Capacitive TouchScreen - /sys/devices/platform/soc@0/44000000.bus/44340000.i2c/i2c-0/0-0014/input/input1/event1
[09:49:27.863] libinput: configuring device "Goodix Capacitive TouchScreen".
[09:49:27.863] input device event1 has no enabled output associated (none named), skipping calibration for now.
[09:49:27.863] libinput: configuring device "44440000.bbnsm:pwrkey".随后，便是真正的显示输出部分，我们这里使用的DSI屏幕将作为Weston显示输出
[09:49:27.864] DRM: head 'DSI-1' updated, connector 35 is connected, EDID make 'unknown', model 'unknown', serial 'unknown'
Supported EOTF modes: SDR
[09:49:27.864] DRM: head 'DSI-1' found, connector 35 is connected, EDID make 'unknown', model 'unknown', serial 'unknown'
Supported EOTF modes: SDR
[09:49:27.864] Registered plugin API 'weston_drm_output_api_v1' of size 32
[09:49:27.864] Color manager: no-op
[09:49:27.864] Module '/usr/lib/libgbm.so' already loaded
[09:49:27.864] Failed to lookup init function: /usr/lib/libgbm.so.1: undefined symbol: gbm_surface_get_in_fence_fd
[09:49:27.865] Output 'DSI-1' attempts EOTF mode: SDR
[09:49:27.865] Output 'DSI-1' using color profile: built-in default sRGB SDR profile
[09:49:27.874] Initialized backlight for head 'DSI-1', device /sys/class/backlight/4ae10000.dsi.0
[09:49:27.874] Output DSI-1 (crtc 33) video modes:
1080x1920@55.0, preferred, current, 121.0 MHz
[09:49:27.874] associating input device event1 with output DSI-1 (none by udev)
[09:49:27.875] associating input device event0 with output DSI-1 (none by udev)
[09:49:27.875] Output 'DSI-1' enabled with head(s) DSI-1log中同时包含DSI显示的部分信息，其connector编号为‘35’，输出显示为1080x1920@55.0 及其他相关信息。这部分信息我们同样可以通过modetest -M imx-drm 命令进行确认。在最后的部分，从log我们可以看到窗口管理(shell)相关的模块被加载。这里可以看到负责系统全局界面的weston-desktop-shell及软键盘面板的weston-keyboard由Weston加载并启动：
[09:49:27.875] Compositor capabilities:
arbitrary surface rotation: yes
screen capture uses y-flip: yes
cursor planes: yes
arbitrary resolutions: no
view mask clipping: yes
explicit sync: yes
color operations: no
presentation clock: CLOCK_MONOTONIC, id 1
presentation clock resolution: 0.000000001 s
[09:49:27.876] Loading module '/usr/lib/weston/desktop-shell.so'
[09:49:27.879] Loading module '/usr/lib/libweston-11/xwayland.so'
[09:49:27.913] Registered plugin API 'weston_xwayland_v1' of size 32
[09:49:27.913] Registered plugin API 'weston_xwayland_surface_v1' of size 16
[09:49:27.913] xserver listening on display :0
[09:49:27.914] Loading module '/usr/lib/weston/systemd-notify.so'
[09:49:27.915] info: add 1 socket(s) provided by systemd
[09:49:27.915] launching '/usr/libexec/weston-keyboard'
[09:49:27.918] launching '/usr/libexec/weston-desktop-shell'在Weston通过自启动服务成功启动之后，Weston桌面便会显示到DSI屏幕上。使用场景方面，例如之前GStreamer文章中，我们使用waylandsink做显示输出至Weston桌面中显示视频画面。我们可以使用以下命令将通过摄像头拍摄的视频使用waylandsink元素将视频画面显示在Weston桌面中。
gst-launch-1.0 v4l2src device=/dev/video3 ! video/x-raw,format=YUY2,width=1920,height=1080 ! waylandsink