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Old 04-07-2010, 08:44 AM   #1
David Li
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Registered: Mar 2010
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DMESG does not display the kernel driver function PRINTK message


Kernel driver function was called via ioctl and returned success, but when I checked the kernel display buffer with dmesg the printk message was not there. Then when you do lsmod, the driver you were calling showed "used by zero". So it seems like the kernel driver was not accessed. In the kernel driver, I had many printk statements, but nothing printed in the buffer.

Can anyone tell me if the driver get accessed and what could cause this?
 
Old 04-07-2010, 10:21 PM   #2
paulsm4
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Registered: Mar 2004
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Sure - a common issue. You probably just need to change the trace level:

http://serverfault.com/questions/247...utput-of-dmesg

http://elinux.org/Kernel_Debugging_Tips

http://www.thelinuxdaily.com/2010/01...rintk-logging/

http://www.developertutorials.com/tu...512/page1.html

Quote:
dmesg -n 9
... or ...

Quote:
echo "9 9 9 9" > /proc/sys/kernel/printk
With the logging defaults, you won't necessarily see anything.

The links I refer to above let you chnage a) the level at which stuff gets logged, b) the level of stuff you see when you read the log, and c) whether or not you see it at the terminal.

'Hope that helps .. PSM

Last edited by paulsm4; 04-07-2010 at 10:31 PM.
 
  


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