/sys/devices/system/ Permission denied

nsp · 01-06-2007, 10:30 PM

Hello everyone,

I am using slackware 11.0 on a laptop computer ThinkPad X31. The kernel is 2.6.17.13-smp from the directory /extra in slackware distribution. When I try to add new files in directories such as /sys/devices/system/.... to control my hardware, such as to adjust the cpu frequency, or to adjust speed of the track point, the system always tell me 'permission denied', even I have logged in as root:

# cp ./speed /sys/devices/platform/i8042/serio0/
bash: /sys/devices/platform/i8042/serio0/speed: Permission denied

I was told that in some other distributions, with the default kernel, this kind of operation is allowed for the root account. So, what's the matter with my kernel?

Another question: I am using 2.6.17.13-smp kernel, but the file /pro/cpuinfo shows that there is only one cpu, not like other distribution's smp kernel, simulating multi processors. So, how can my kernel support simulating multi processors?

Should I recompile the kernel? I don't try it yet. Is it necessary? And is it difficult?

Sorry for my English. Thanks for your attention.

H_TeXMeX_H · 01-06-2007, 10:34 PM

Is there already a file at location
"/sys/devices/platform/i8042/serio0/speed"
?

If so, then back it up (change permissions if necessary) and then delete it (as long as you know what you are doing).

If that doesn't work, check the permissions of each folder and file in that path: i.e.
/sys
/sys/devices
/sys/..............

oh, and post the output of:

Code:

cat /proc/cpuinfo

nsp · 01-06-2007, 10:47 PM

Quote:

Originally Posted by H_TeXMeX_H

Is there already a file at location
"/sys/devices/platform/i8042/serio0/speed"
?

If so, then back it up (change permissions if necessary) and then delete it (as long as you know what you are doing).

If that doesn't work, check the permissions of each folder and file in that path: i.e.
/sys
/sys/devices
/sys/..............

oh, and post the output of:

Code:

cat /proc/cpuinfo

Thank you.

Sorry I am surfing internet not on my own computer, so I can't answer all of them on-line. By my memory, I can tell:

1. There is no "/sys/devices/platform/i8042/serio0/speed" file already.

2. I can tell "/sys/devices/platform/i8042/serio0/" is writable for root account for I have checked it. But I am not sure what about its parent directories: "/sys", "/sys/devices",...

3. I'll post the output of /proc/cpuinfo later.

Thanks again.

nsp · 01-06-2007, 11:28 PM

H_TeXMeX_H,

I have checked my computer, now I can answer this:

1. All of the directories
/sys
/sys/devices
.....

are "drwxr-xr-x", so they are writable for root account.

2. about /proc/cpuinfo

Code:

$ cat /proc/cpuinfo 
processor       : 0
vendor_id       : GenuineIntel
cpu family      : 6
model           : 9
model name      : Intel(R) Pentium(R) M processor 1700MHz
stepping        : 5
cpu MHz         : 1700.000
cache size      : 1024 KB
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 2
wp              : yes
flags           : fpu vme de pse tsc msr mce cx8 sep mtrr 
                  pge mca cmov pat clflush dts acpi mmx fxsr
                  sse sse2 tm pbe up est tm2
bogomips        : 3418.24

Thanks

H_TeXMeX_H · 01-07-2007, 12:10 AM

AFAIK the "Intel(R) Pentium(R) M processor 1700MHz" is NOT HT compatible, and definitely not dual core. Thus, you are seeing one CPU because that is the truth ... you shouldn't even be running the SMP kernel. The SMP kernel is pretty much just for Pentium 4s with HT enabled (and, if they exist (I don't know of any), other 32-bit Intel processors with more than one core (virtual or real)).

As for the /sys directory, some of the things in there may be in use (I just checked the directory you were referring to and get the same result), so if you really must change them try booting from a live CD and then changing things from there.

jonnycando · 01-07-2007, 08:40 AM

Quote:

Originally Posted by H_TeXMeX_H

AFAIK the "Intel(R) Pentium(R) M processor 1700MHz" is NOT HT compatible, and definitely not dual core. Thus, you are seeing one CPU because that is the truth ... you shouldn't even be running the SMP kernel. The SMP kernel is pretty much just for Pentium 4s with HT enabled (and, if they exist (I don't know of any), other 32-bit Intel processors with more than one core (virtual or real)).

As for the /sys directory, some of the things in there may be in use (I just checked the directory you were referring to and get the same result), so if you really must change them try booting from a live CD and then changing things from there.

If he has the Pentium M number 780, he has what Intel calls "Dual Core technology." and they have them 1.7 to 2.26 Ghz.

H_TeXMeX_H · 01-07-2007, 12:13 PM

Here is your processor:

http://processorfinder.intel.com/det...px?sSpec=SL6N9

Here is a Pentium 4 with HT (for example):

http://processorfinder.intel.com/det...px?sSpec=SL8PY

Show me where it says the "Intel(R) Pentium(R) M processor 1700MHz" is HT capable.

jonnycando · 01-07-2007, 08:59 PM

Quote:

Originally Posted by H_TeXMeX_H

Here is your processor:

http://processorfinder.intel.com/det...px?sSpec=SL6N9

Here is a Pentium 4 with HT (for example):

http://processorfinder.intel.com/det...px?sSpec=SL8PY

Show me where it says the "Intel(R) Pentium(R) M processor 1700MHz" is HT capable.

I don't contend it is. But at the risk of being wrong, if you can have one in Dual core, does that not obviate any advantage of HT? And would the SMP kernel not be useful with a Dual Core processor. My specific ingnorance here based on the fact that I am still single core over here in the hills, heck we just got electric lights.

H_TeXMeX_H · 01-07-2007, 11:36 PM

Well, if indeed it is dual core, the smp kernel should work and you should see both cores in /proc/cpuinfo. All the info I have so far suggests that the processor nsp has is neither dual-core nor does it support hyperthreading (HT) and does not show two cores in /proc/cpuinfo.

nsp · 01-09-2007, 04:57 AM

H_TeXMeX_H and jonnycando,

Thank you for your posts. I think now I have some ideas about smp and "HT flag".

But for the first question about changing or creating files in /sys/devices/..., I still think there is something unnormal in my system, because others can do it directly:

http://www.thinkwiki.org/wiki/How_to...the_TrackPoint

http://www.thinkwiki.org/wiki/How_to...quency_Scaling

The later page is for changing cpu frequency. It tells that the command:

Code:

# echo 900000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed

will work, but I failed it. There is a file "/sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed" already there.

But I can do this kind of operation:

Code:

# cp /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_min_freq 
     /sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed

And it works well. Both of the two files already exist.

Thanks again.

H_TeXMeX_H · 01-09-2007, 06:48 PM

Well, I'm betting that some of the directories in there are in use by the kernel (not sure, but have no other ideas). Try booting into a live CD and changing it from there, then boot back in normally.

Anyone else have any idea, I'm out of them.

nsp · 01-11-2007, 05:05 AM

H_TeXMeX_H,

I think that your method will work, but don't fit for me, for I am trying to change or add files while my system is running, such as to change CPU frequency on-line. I will try to find other ways. Thank you anyway.

nsp

H_TeXMeX_H · 01-11-2007, 01:10 PM

Quote:

Originally Posted by nsp

H_TeXMeX_H,

I think that your method will work, but don't fit for me, for I am trying to change or add files while my system is running, such as to change CPU frequency on-line. I will try to find other ways. Thank you anyway.

nsp

Best way to do it is with cpufreq or cpu_freq_throttle
(uses cpufreq).

nsp · 01-12-2007, 07:14 AM

Thank you, I'll try it.

Regards