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Message-ID: <488e8eed-e0f0-4055-b43c-5422b6302632@roeck-us.net>
Date: Tue, 14 May 2024 12:47:55 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: "Chatradhi, Naveen Krishna" <naveenkrishna.chatradhi@....com>,
Naveen Krishna Chatradhi <nchatrad@....com>, linux-hwmon@...r.kernel.org,
linux-kernel@...r.kernel.org
Cc: Akshay Gupta <Akshay.Gupta@....com>, arnd@...db.de, lee@...nel.org,
gregkh@...uxfoundation.org
Subject: Re: [PATCH 2/2] sbrmi: Add support for APML protocols
On 5/14/24 12:15, Chatradhi, Naveen Krishna wrote:
> + @Misc and @MFD maintainers in CC
>
> Hi
>
> On 5/3/2024 3:56 AM, Guenter Roeck wrote:
>> Caution: This message originated from an External Source. Use proper caution when opening attachments, clicking links, or responding.
>>
>>
>> On 5/2/24 15:05, Naveen Krishna Chatradhi wrote:
>>> From: Naveen Krishna Chatradhi <naveenkrishna.chatradhi@....com>
>>>
>>> The present sbrmi module only support reporting power. However, AMD data
>>> center processors support various system management functionality
>>> Out-of-band over Advanced Platform Management Link APML.
>>>
>>> Register a miscdevice, which creates a device /dev/sbrmiX with an IOCTL
>>> interface for the user space to invoke the following protocols.
>>> - Mailbox read/write (already defined in sbrmi_mailbox_xfer())
>>> - CPUID read
>>> - MCAMSR read
>>>
>>
>> This is not hardware monitoring functionality and would have to reside
>> elsewhere, outside the hwmon subsystem.
>
> I thought as much, please provide your opinion on the following approach.
>
> Background: Present sbrmi under hwmon subsystem is probed as an i2c driver and reports power.
>
> However, APML interface defines few other protocols to support OOB system management functionality.
>
> As adding the core functionality of the APML interface in drivers/hwmon/sbrmi is not the correct approach.
>
> We would like do the following
>
> 1. Move the i2c client probe, misc device registration and rmi_mailbox_xfer() function to a drivers/misc.
>
> 2. Add an MFD device with a cell, which probes the hwmon/sbrmi and continues to report power using the symbols exported by the misc/sbrmi.
>
afaik mfd API function must not be used outside drivers/mfd. The mfd maintainer
is (or at least used to be) pretty strict on that. The core code of a
multi-function device might better be implemented in drivers/mfd, with
drivers in drivers/misc (for the misc device) and drivers/hwmon/ (for
hwmon functionality). The misc and hwmon drivers could then communicate
with the core using regmap.
drivers/mailbox/ supports mailbox style communication. I don't know if that
would apply to the mailbox functionality implemented here.
Guenter
> 3. Define an ioctl for user-space to access other system management functionality.
>
> a. The open-sourced https://github.com/amd/esmi_oob_library will continue to provide user space programmable API
>
> Regards,
>
> naveenk
>
>>
>> Guenter
>>
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