linux-kernel - Re: [PATCH 1/3] watchdog: make Siemens Simatic watchdog driver default on platform

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Date:   Wed, 19 Jul 2023 06:27:19 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Henning Schild <henning.schild@...mens.com>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Lee Jones <lee@...nel.org>,
        Hans de Goede <hdegoede@...hat.com>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        linux-kernel@...r.kernel.org, linux-leds@...r.kernel.org,
        platform-driver-x86@...r.kernel.org,
        linux-watchdog@...r.kernel.org, Pavel Machek <pavel@....cz>,
        Mark Gross <markgross@...nel.org>,
        Tobias Schaffner <tobias.schaffner@...mens.com>
Subject: Re: [PATCH 1/3] watchdog: make Siemens Simatic watchdog driver
 default on platform

On 7/19/23 00:18, Henning Schild wrote:
> Am Tue, 18 Jul 2023 08:10:09 -0700
> schrieb Guenter Roeck <linux@...ck-us.net>:
> 
>> On 7/18/23 07:42, Henning Schild wrote:
>>> Am Tue, 18 Jul 2023 17:20:48 +0300
>>> schrieb Andy Shevchenko <andriy.shevchenko@...ux.intel.com>:
>>>    
>>>> On Tue, Jul 18, 2023 at 12:52:11PM +0200, Henning Schild wrote:
>>>>> If a user did choose to enable Siemens Simatic platform support
>>>>> they likely want that driver to be enabled without having to flip
>>>>> more config switches. So we make the watchdog driver config switch
>>>>> default to the platform driver switches value.
>>>>
>>>> A nit-pick below.
>>>>
>>>> ...
>>>>   
>>>>>    config SIEMENS_SIMATIC_IPC_WDT
>>>>>    	tristate "Siemens Simatic IPC Watchdog"
>>>>>    	depends on SIEMENS_SIMATIC_IPC
>>>>   
>>>>> +	default SIEMENS_SIMATIC_IPC
>>>>
>>>> It's more natural to group tristate and default, vs. depends and
>>>> select.
>>>
>>> Will be ignored unless maintainer insists.
>>>    
>>
>> Maintainer wants to know why "default SIEMENS_SIMATIC_IPC" is needed
>> or warranted instead of the much simpler and easier to understand
>> "default y".
> 
> I thought a "default y" or "default m" was maybe not the best idea for
> a platform that is not super common. That is why i did not dare to even
> think about defaulting any of the Simatic stuff to not-no.
> 
> But it seems that this would be ok after all. And i would be very happy
> to do so because it means less work on distro configs.
> 
> SIEMENS_SIMATIC_IPC_WDT will drive a platform device which gets
> registered by SIEMENS_SIMATIC_IPC and nothing else. That is why
> "default SIEMENS_SIMATIC_IPC" was chosen.
> 

It depends on SIEMENS_SIMATIC_IPC. "default y" would make it y if
SIEMENS_SIMATIC_IPC=y, and m if SIEMENS_SIMATIC_IPC=m. If
SIEMENS_SIMATIC_IPC=n, it won't even be offered as option, and
default={m,y} will be ignored.

> But if i may i would change that to "default m", not "y" because there
> is an out of tree driver package which if installed on top, should be
> able to override the in-tree drivers.
> 
> So i will go ahead and make that one "default m"
> 

Why make it m as default even if SIEMENS_SIMATIC_IPC=y for whatever
reason ? Presumably anyone selecting SIEMENS_SIMATIC_IPC=y would
also want SIEMENS_SIMATIC_IPC_WDT=y, which is what you had before.
Sorry, I don't understand your logic.

Guenter