Linux DRM那些事-libdrm调试准备

本文主要介绍libdrm的代码下载、编译和调试前的准备工作。

一、代码下载

libdrm下载网址：https://dri.freedesktop.org/libdrm/libdrm-2.4.89.tar.bz2

解压命令：tar -jxvf libdrm-2.4.89.tar.bz2

在代码解压后，可以使用git命令创建本地git仓，方便代码管理，创建方法后续介绍。

二、代码编译

代码完成解压后，按如下命令编译：

 

./configure --prefix=/opt/ --host=aarch64-linux-gnu
make && make install
## 编译删除
make distclean

1、configure参数

1）--prefix：配置软件安装目录，可以配置。

2）--build：指定编译代码的主机，可以不配置。

3）--host：指定编译后的运行主机，需要配置和单板使用相同的编译工具链前缀。

4）--enable-udev：使用Udev代替mknod，一定不要配置。

5）./configure --help查看参数用法。

2、编译映像

编译后映像：libdrm-2.4.89/.libs/libdrm.so.2.4.0和libdrm-2.4.89/tests/modetest/.libs/modetest。

其它测试命令(如：proptest)路径类似。

三、调试问题

1、调试准备

如使用modetest测试，需要拷贝modetest和libdrm.so.2.4.0，方法：

 

## 文件存在U盘中
mount /dev/sda4 /tmp/
cp /tmp/modetest ~/
chmod 777 modetest
cd /usr/lib/aarch64-linux-gnu
rm libdrm.so
cp /tmp/libdrm.so.2.4.0 .
ln -s libdrm.so.2.4.0 libdrm.so
cd ~
./modetest

2、--host设置错误

libdrm编译时，如果--host设置错误，在单板上使用modetest命令时，会提示如下错误：

 

cannot execute binary file: Exec format error

3、编译时添加--enable-udev

libdrm编译时，如果添加--enable-udev，在单板上使用modetest命令时，会提示如下错误：

 

root@linaro-alip:~# ./modetest
trying to open device 'rockchip'...drmOpenDevice: node name is /dev/dri/card0
drmOpenDevice: node name is /dev/dri/card0
drmOpenDevice: node name is /dev/dri/card1
drmOpenDevice: node name is /dev/dri/card2
drmOpenDevice: node name is /dev/dri/card3
drmOpenDevice: node name is /dev/dri/card4
drmOpenDevice: node name is /dev/dri/card5
drmOpenDevice: node name is /dev/dri/card6
drmOpenDevice: node name is /dev/dri/card7
drmOpenDevice: node name is /dev/dri/card8
drmOpenDevice: node name is /dev/dri/card9
drmOpenDevice: node name is /dev/dri/card10
drmOpenDevice: node name is /dev/dri/card11
drmOpenDevice: node name is /dev/dri/card12
drmOpenDevice: node name is /dev/dri/card13
drmOpenDevice: node name is /dev/dri/card14
drmOpenDevice: node name is /dev/dri/card15
failed
no device found

4、no device found

modetest测试失败信息如下：

 

root@linaro-alip:~# ./modetest
trying to open device 'rockchip'...failed
...
no device found

有的平台会显示Permission denied错误。

原因：/dev/dri/card0被占用。

需要关闭系统原有的显示进程，方法：

 

root@linaro-alip:~# ps -APID TTY          TIME CMD1 ?        00:00:03 systemd...958 tty7     00:00:00 Xorg      ## 显示进程...## 如果一次没有kill Xorg成功，多试几次
root@linaro-alip:~# killall Xorg && ./modetest
trying to open device 'rockchip'...failed
...
no device found## 此时可成功使用modetest测试。
root@linaro-alip:~#killall Xorg && ./modetest
trying to open device 'rockchip'...done
Encoders:
id      crtc    type    possible crtcs  possible clones
87      0       TMDS    0x00000001      0x00000000Connectors:
id      encoder status          name            size (mm)       modes   encoders
88      0       disconnected    HDMI-A-1        0x0             0       87props:1 EDID:flags: immutable blobblobs:value:2 DPMS:flags: enumenums: On=0 Standby=1 Suspend=2 Off=3value: 089 hdmi_output_depth:flags: enumenums: Automatic=0 24bit=8 30bit=10value: 890 hdmi_output_format:

5、modetest测试

在单板上使用modetest命令运行成功时，会出现下列日志：

 

root@linaro-alip:~# ./modetest
trying to open device 'i915'...failed
trying to open device 'amdgpu'...failed
trying to open device 'radeon'...failed
trying to open device 'nouveau'...failed
trying to open device 'vmwgfx'...failed
trying to open device 'omapdrm'...failed
trying to open device 'exynos'...failed
trying to open device 'tilcdc'...failed
trying to open device 'msm'...failed
trying to open device 'sti'...failed
trying to open device 'tegra'...failed
trying to open device 'imx-drm'...failed
trying to open device 'rockchip'...done
Encoders:
id      crtc    type    possible crtcs  possible clones
87      0       TMDS    0x00000001      0x00000000Connectors:
id      encoder status          name            size (mm)       modes   encoders
88      0       disconnected    HDMI-A-1        0x0             0       87props:1 EDID:flags: immutable blobblobs:value:2 DPMS:flags: enumenums: On=0 Standby=1 Suspend=2 Off=3value: 089 hdmi_output_depth:flags: enumenums: Automatic=0 24bit=8 30bit=10value: 890 hdmi_output_format:flags: enumenums: output_rgb=0 output_ycbcr444=1 output_ycbcr422=2 output_ycbcr420=3 output_ycbcr_high_subsampling=4 output_ycbcr_low_subsampling=5 invalid_output=6value: 0...

在上面的log中，打开其它平台DRM名称（如：i915）时失败，可通过修改代码消除，方法如下：

 

## 把rockchip放到modules的第一位即可或modules中只保留rockchip
static const char * const modules[] = {"rockchip","i915","amdgpu","radeon","nouveau","vmwgfx","omapdrm","exynos","tilcdc","msm","sti","tegra","imx-drm","atmel-hlcdc","fsl-dcu-drm","vc4","virtio_gpu","mediatek","meson","pl111",
};

注：本文基于RockPI 4A单板Debian映像调试。

注 2：本文只是验证lib库的编译，移植未做验证。