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SubjectHelp: Using cpufreq from kernel level
Date
Hi all,

I'm writing a kernel module that needs to get info about the available
frequencies on the current processor and to periodically change the current
frequency.

At user level it can be done through

/sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies
/sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_cur_freq
/sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed

but I have no idea how to implement it at kernel level.

I tried to declare

extern struct cpufreq_driver *cpufreq_driver;
extern struct cpufreq_policy *cpufreq_cpu_data[NR_CPUS];
extern spinlock_t cpufreq_driver_lock;
extern ssize_t show_available_freqs (struct cpufreq_policy *policy, char
*buf);

and to do

char buffer [100000] = "\n";
spin_lock_irqsave(&cpufreq_driver_lock, flags);
show_available_freqs(cpufreq_cpu_data[0], buffer);
spin_unlock_irqrestore(&cpufreq_driver_lock, flags);

but it crashes the system.

Please, can somebody tell me how this can be done ?

Many thanks,

Claudio Scordino
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