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SubjectRe: [PATCH 1/3 v6] cpufreq: Add debugfs directory for cpufreq
On 07/24/2013 05:07 PM, Viresh Kumar wrote:
> I just realized I missed answering few questions:
>
> On 24 July 2013 13:13, Chanwoo Choi <cw00.choi@samsung.com> wrote:
>> On 07/24/2013 02:05 PM, Viresh Kumar wrote:
>>> On 24 July 2013 06:55, Chanwoo Choi <cw00.choi@samsung.com> wrote:
>>>> On 07/22/2013 07:11 PM, Viresh Kumar wrote:
>>>>> On 18 July 2013 16:47, Chanwoo Choi <cw00.choi@samsung.com> wrote:
>
>>>>>> +static void cpufreq_move_debugfs_dir(struct cpufreq_policy *policy,
>>>>>> + unsigned int new_cpu)
>>>>>> +{
>>>>>> + struct dentry *old_entry, *new_entry;
>>>>>> + char new_dir_name[CPUFREQ_NAME_LEN];
>>>>>> + unsigned int j, old_cpu = policy->cpu;
>>>>>> +
>>>>>> + if (!policy->cpu_debugfs[new_cpu])
>>>>>> + return;
>>>>>> +
>>>>>> + /*
>>>>>> + * Remove symbolic link of debugfs directory except for debugfs
>>>>>> + * directory of old_cpu.
>>>>>> + */
>>>>>> + for_each_present_cpu(j) {
>>>>>> + if (old_cpu == j)
>>>>>> + continue;
>>>>>> +
>>>>>> + debugfs_remove(policy->cpu_debugfs[j]);
>>>>>
>>>>> Why you need this? We aren't removing the earlier dentry at all here.
>>>
>>> haven't answered this.
>>
>> The debugfs entry of 'old_cpu' include child debugfs file(e.g., load_table)
>> If cpu is last user of policy and core call __cpufre_remove_dev() to remove last cpu,
>> core call cpufreq_move_debugfs_dir(). I have to move the data of debugfs directory/file and
>> child data for 'old_cpu' to debugfs directory for 'new_cpu'.
>>
>> If I remove earlier dentry of 'old_cpu', I can't get the child debugfs dir/file.
>> So I didn't remove the earlier dentry of 'old_cpu'.
>
> Okay.. The original question was: why do you need to remove & add
> entries or links for cpus other than policy->cpu? Because we are renaming
> the entry, wouldn't that work straight away?
>

In case that all CPUs share same cpufreq policy. Each debugfs dentry of CPU[1-3]
except for CPU0 has symbolic link to CPU0's debugfs directory as following.

-sh-4.1# ls -al /sys/kernel/debug/cpufreq/
total 0
drwxr-xr-x 3 root root 0 Jan 1 09:00 .
drwx------ 28 root root 0 Jan 1 09:00 ..
drwxr-xr-x 2 root root 0 Jan 1 09:00 cpu0 (policy->cpu is 0)
lrwxrwxrwx 1 root root 0 Jan 1 09:00 cpu1 -> ./cpu0
lrwxrwxrwx 1 root root 0 Jan 1 09:00 cpu2 -> ./cpu0
lrwxrwxrwx 1 root root 0 Jan 1 09:00 cpu3 -> ./cpu0

If turn off CPU0 state, I have to move debugfs directory data from cpu0 to cpu1
and again create link to cpu1's debugfs directory for CPU[2-3] debugfs directory.
So, I removed dentry link of CPU[1-3] before creating link again.

cpu1
cpu2 -> ./cpu1
cpu3 -> ./cpu1

But I can rewrite new link of CPU[2-3] to previous dentry link(policy->cpu_debugfs[2] or policy->cpu_debugfs[3])
for reducing unnecessary code without revmoval sequence.





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