linux-kernel - Re: [PATCH v3 3/6] hwmon: (pmbus/core) add wp module param

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Message-ID: <0d9f1a5a-aa1d-4e99-8df7-3deb08433dc1@roeck-us.net>
Date: Mon, 4 Nov 2024 05:57:17 -0800
From: Guenter Roeck <linux@...ck-us.net>
To: Jerome Brunet <jbrunet@...libre.com>
Cc: Jean Delvare <jdelvare@...e.com>, Jonathan Corbet <corbet@....net>,
 Patrick Rudolph <patrick.rudolph@...ements.com>,
 Naresh Solanki <naresh.solanki@...ements.com>, Rob Herring
 <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>,
 Delphine CC Chiu <Delphine_CC_Chiu@...ynn.com>, linux-hwmon@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
 devicetree@...r.kernel.org, linux-i2c@...r.kernel.org
Subject: Re: [PATCH v3 3/6] hwmon: (pmbus/core) add wp module param

On 11/4/24 00:43, Jerome Brunet wrote:
> On Fri 01 Nov 2024 at 08:08, Guenter Roeck <linux@...ck-us.net> wrote:
> 
>> On Thu, Oct 24, 2024 at 08:10:37PM +0200, Jerome Brunet wrote:
>>> Add a module parameter to force the write protection mode of pmbus chips.
>>>
>>> 2 protections modes are provided to start with:
>>> * 0: Remove the write protection if possible
>>> * 1: Enable full write protection if possible
>>>
>>> Of course, if the parameter is not provided, the default write protection
>>> status of the pmbus chips is left untouched.
>>>
>>> Suggested-by: Guenter Roeck <linux@...ck-us.net>
>>> Signed-off-by: Jerome Brunet <jbrunet@...libre.com>
>>> ---
>>>   Documentation/admin-guide/kernel-parameters.txt |  4 ++
>>>   drivers/hwmon/pmbus/pmbus_core.c                | 74 ++++++++++++++++++-------
>>>   2 files changed, 59 insertions(+), 19 deletions(-)
>>>
>>> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
>>> index 1518343bbe2237f1d577df5656339d6224b769be..aa79242fe0a9238f618182289f18563ed63cba1c 100644
>>> --- a/Documentation/admin-guide/kernel-parameters.txt
>>> +++ b/Documentation/admin-guide/kernel-parameters.txt
>>> @@ -4733,6 +4733,10 @@
>>>   			Format: { parport<nr> | timid | 0 }
>>>   			See also Documentation/admin-guide/parport.rst.
>>>   
>>> +	pmbus.wp=	[HW] PMBus Chips write protection forced mode
>>> +			Format: { 0 | 1 }
>>> +			See drivers/hwmon/pmbus/pmbus_core.c
>>> +
>>
>> I have always seen that file as applicable for core kernel parameters,
>> not for driver kernel parameters. I can not accept a global change like
>> this without guidance. Please explain why it is desirable to have this
>> parameter documented here and not in driver documentation.
> 
> No reason other than trying to document things the best I can.
> Other subsystemw are documenting things in here too, I just did the same
> 
> See 'regulator_ignore_unused' for example.
> 

Basic rule: You can find examples for everything in the kernel, including
dell_smm_hwmon in the same file. That doesn't make it better. It only shows
that I did not pay attention. Trying to add all the other 80+ module
parameters of hwmon drivers, or all the 5,000+ module parameters from all
drivers, into the same file would not scale well.

Please document the module parameter in Documentation/hwmon/pmbus-core.rst.

Thanks,
Guenter