Re: [PATCH v2 0/5] Introduce AMD PMF util layer and user-space interface for SystemDeck

[Mario Limonciello <mario.limonciello@amd.com>]

On 11/19/25 10:20 AM, Hans de Goede wrote:
> Hi Shyam,
> 
> On 11-Nov-25 8:10 AM, Shyam Sundar S K wrote:
>> This series introduces a util layer to the AMD Platform Management
>> Framework (PMF) and a minimal user-space interface via a misc character
>> device, enabling feature discovery and smoother integration with
>> user-space tools. It also adds caching of BIOS output policy values to
>> prepare for user-space telemetry reporting via IOCTLs.
>>
>> The motivation is to provide a stable interface for user-space tools to
>> discover PMF features and consume selected metrics. Enable smoother
>> integration with AMD SystemDeck
> 
> This does not really explain why you've chosen for a new character-device
> with IOCTLs instead of sysfs where as so far (AFAICT) all the AMD PMF code
> has been using sysfs APIs.
> 
> Is there any specific reason why to switch to IOCTLs all of a sudden?
> 
> Note that:
> 
> 1. sysfs APIs can be (and must be) stable too, sysfs APIs are not allowed
> to be changed once shipped in a stable kernel.
> 2. sysfs attributes can be used with poll() to so if you want to do
> notifications of changes that can be done through sysfs too.
> 
> Note I'm not saying you must use sysfs, but so far the PMF code has been
> using sysfs everywhere and this new IOCTL based API is not really consistent
> with this.

Isn't there only one sysfs file for turning on/off CNQF?

> 
> So at a minimum you are going to need some pretty good arguments to
> deviate from just doing this with sysfs as has been done before.
> 
> Regards,
> 
> Hans
> 
> 
> 
> 
>> , a widely used tool for monitoring and
>> controlling power and thermal behavior, helping designers keep components
>> within thermal limits to ensure proper operation and improve system
>> stability and reliability.
>>
>> This series also adds a small, dependable userspace utility that leverages
>> the new IOCTLs to query live power and thermal telemetry. Exposing this
>> data in a scriptable interface helps users and tooling make informed,
>> workload-aware decisions and supports validation and debugging.
>>
>> v2:
>> ----
>>   - address remarks from v1
>>   - add a new tool that exercises the IOCTLs from PMF interface
>>
>> Shyam Sundar S K (5):
>>    platform/x86/amd/pmf: add util layer and user-space misc device
>>      interface
>>    platform/x86/amd/pmf: cache BIOS output values for user-space
>>      telemetry via util IOCTL
>>    Documentation/ABI: add testing entry for AMD PMF misc device interface
>>    platform/x86/amd/pmf: Store commonly used enums in the header file
>>    platform/x86/amd/pmf: Introduce AMD PMF testing tool for driver
>>      metrics and features
>>
>>   .../ABI/testing/misc-amdpmf_interface         |  49 +++
>>   MAINTAINERS                                   |   1 +
>>   drivers/platform/x86/amd/pmf/Kconfig          |  10 +
>>   drivers/platform/x86/amd/pmf/Makefile         |   2 +
>>   drivers/platform/x86/amd/pmf/core.c           |  19 +
>>   drivers/platform/x86/amd/pmf/pmf.h            |  33 +-
>>   drivers/platform/x86/amd/pmf/spc.c            |   1 +
>>   drivers/platform/x86/amd/pmf/tee-if.c         |  10 +
>>   drivers/platform/x86/amd/pmf/util.c           | 236 +++++++++++
>>   include/uapi/linux/amd-pmf.h                  |  96 +++++
>>   tools/testing/selftests/Makefile              |   1 +
>>   .../drivers/platform/x86/amd/pmf/Makefile     |   8 +
>>   .../drivers/platform/x86/amd/pmf/test_pmf.c   | 388 ++++++++++++++++++
>>   13 files changed, 832 insertions(+), 22 deletions(-)
>>   create mode 100644 Documentation/ABI/testing/misc-amdpmf_interface
>>   create mode 100644 drivers/platform/x86/amd/pmf/util.c
>>   create mode 100644 include/uapi/linux/amd-pmf.h
>>   create mode 100644 tools/testing/selftests/drivers/platform/x86/amd/pmf/Makefile
>>   create mode 100644 tools/testing/selftests/drivers/platform/x86/amd/pmf/test_pmf.c
>>
>