Re: [PATCH 1/4] drivers core: Introduce CPU type sysfs interface

[Randy Dunlap]

On 10/5/20 6:15 PM, Ricardo Neri wrote:
> On Fri, Oct 02, 2020 at 08:27:41PM -0700, Randy Dunlap wrote:
>> On 10/2/20 6:17 PM, Ricardo Neri wrote:
>>> +/**
>>> + * arch_get_cpu_type() - Get the CPU type number
>>> + * @cpu:	Index of the CPU of which the index is needed
>>> + *
>>> + * Get the CPU type number of @cpu, a non-zero unsigned 32-bit number that
> 
> Thank you for your feedback Randy!
> 
>> Are you sure that @cpu is non-zero?
> 
> This is the intent. Maybe it can be reworked to return -EINVAL instead?
> I gues it is plausible but less likely that an arch defines a type as
> 0xffffffea;

You lost me here.

>>
>>> + * uniquely identifies a type of CPU micro-architecture. All CPUs of the same
>>> + * type have the same type number. Type numbers are defined by each CPU
>>> + * architecture.
>>> + */
>>> +u32 __weak arch_get_cpu_type(int cpu)
>>> +{
>>> +	return 0;
>>> +}
>>
>> arch_get_cpu_type() in patch 4/4 allows @cpu to be 0.
> 
> It should not return 0 if the system does not have
> X86_FEATURE_HYBRID_CPU. The currently existing CPU types are all
> non-zero as per the Intel SDM. Am I missing anything?

@cpu is a cpu index, not a cpu type.

-- 
~Randy