[lkml]   [2005]   [Dec]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: Help: Using cpufreq from kernel level
Claudio Scordino wrote:
> 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 ?

For one thing, you cannot put such a huge buffer on the kernel stack.

Robert Hancock Saskatoon, SK, Canada
To email, remove "nospam" from
Home Page:

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2005-12-17 19:30    [W:0.025 / U:1.584 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site