drm_debug是cmdline参数,可以trace相关日志,阅读gpu驱动代码时,会非常有效。

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unsigned int drm_debug = 0;
EXPORT_SYMBOL(drm_debug);
 
MODULE_AUTHOR("Gareth Hughes, Leif Delgass, Jos?Fonseca, Jon Smirl");
MODULE_DESCRIPTION("DRM shared core routines");
MODULE_LICENSE("GPL and additional rights");
MODULE_PARM_DESC(debug, "Enable debug output, where each bit enables a debug category.\n"
"\t\tBit 0 (0x01)  will enable CORE messages (drm core code)\n"
"\t\tBit 1 (0x02)  will enable DRIVER messages (drm controller code)\n"
"\t\tBit 2 (0x04)  will enable KMS messages (modesetting code)\n"
"\t\tBit 3 (0x08)  will enable PRIME messages (prime code)\n"
"\t\tBit 4 (0x10)  will enable ATOMIC messages (atomic code)\n"
"\t\tBit 5 (0x20)  will enable VBL messages (vblank code)\n"
"\t\tBit 7 (0x80)  will enable LEASE messages (leasing code)\n"
"\t\tBit 8 (0x100) will enable DP messages (displayport code)");
module_param_named(debug, drm_debug, int, 0600);

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//if want to trace DRM_DEBUG_KMS and DRM_DEBUG_DRIVER log
 drm.debug=0x6