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Linux Kernel • VC4 Debugging

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I downloaded the rpi linux kernel source, and added some custom debug messages functions using pr_debug in the vc4_dsi.c driver

I also modified the .config file
CONFIG_DEBUG_FS=y
CONFIG_DYNAMIC_DEBUG=y

then i compiled the vc4 module and replaced the old vc4.ko.xz module with the new vc4.ko file,
but no matter what I try, i just cannot see my custom debug messages on dmesg

I also added this to the cmdline.txt:

Code:

dyndbg="file /home/pi/linux/drivers/gpu/drm/vc4/vc4_dsi.c +p" loglevel=8 vc4.debug=0x1ff
dmesg | grep vc4:

Code:

[    0.000000] Unknown kernel command line parameters "dyndbg=file /home/pi/linux/drivers/gpu/drm/vc4/vc4_dsi.c +p", will be passed to user space.[    2.843931]     dyndbg=file /home/pi/linux/drivers/gpu/drm/vc4/vc4_dsi.c +p[    3.003227] vc4: unknown parameter 'debug' ignored

Statistics: Posted by ORR — Wed Aug 20, 2025 2:29 pm — Replies 1 — Views 102



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