linux-kernel - Re: [PATCH v1 2/3] cpufreq: Always enforce policy limits even without frequency table

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Message-ID: <67b55ae1-60b0-4d54-8220-59f7e3ba7c29@kylinos.cn>
Date: Mon, 8 Sep 2025 15:08:50 +0800
From: Zihuan Zhang <zhangzihuan@...inos.cn>
To: Viresh Kumar <viresh.kumar@...aro.org>
Cc: "Rafael J . wysocki" <rafael@...nel.org>,
 Saravana Kannan <saravanak@...gle.com>, zhenglifeng
 <zhenglifeng1@...wei.com>, linux-pm@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 2/3] cpufreq: Always enforce policy limits even without
 frequency table

在 2025/9/8 14:55, Viresh Kumar 写道:
> On 08-09-25, 14:51, Zihuan Zhang wrote:
>> We are currently considering moving the check that ensures a driver
>> providing a freq_table also implements target_index() into the driver
>> registration path.
> That won't work AFAIU. The freq table is initialized during
> policy->init and that's not done at the time of registration.

One idea we are considering is to check whether driver->verify points to 
cpufreq_generic_frequency_table_verify and use that as a heuristic to 
enforce the presence of target_index():

  ((driver_data->verify == cpufreq_generic_frequency_table_verify) != 
!!driver_data->target_index)

I haven’t tested this approach yet, so I’m not sure if it will be fully 
reliable.

>> This way, freq_table.c no longer needs to defensively check for NULL
>> pointers.
>>
>> Additionally, we are thinking about merging the two related APIs into a
>> single one. Do you think this is a good idea?
> Which ones ? target/target_index ? I am not sure if that can be done.

If this approach 
works,  cpufreq_generic_frequency_table_verify and cpufreq_frequency_table_verify 
should be the same because we dont't need to check pointer is NULL  in 
freq_table.c.

> We are fine with improvements generally, but please make sure whatever
> you send doesn't break existing users. That will help saving some of
> our review time.