linux-kernel - Re: [PATCH v2 2/3] leds: simatic-ipc-leds-gpio: split up into multiple drivers

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Message-ID: <20230302180632.289c9e9b@md1za8fc.ad001.siemens.net>
Date:   Thu, 2 Mar 2023 18:06:32 +0100
From:   Henning Schild <henning.schild@...mens.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Pavel Machek <pavel@....cz>, Lee Jones <lee@...nel.org>,
        Hans de Goede <hdegoede@...hat.com>,
        Mark Gross <markgross@...nel.org>,
        linux-kernel@...r.kernel.org, linux-leds@...r.kernel.org,
        platform-driver-x86@...r.kernel.org
Subject: Re: [PATCH v2 2/3] leds: simatic-ipc-leds-gpio: split up into
 multiple drivers

Am Thu, 2 Mar 2023 18:21:21 +0200
schrieb Andy Shevchenko <andriy.shevchenko@...ux.intel.com>:

> On Thu, Mar 02, 2023 at 04:58:24PM +0100, Henning Schild wrote:
> > Am Thu, 2 Mar 2023 17:46:54 +0200
> > schrieb Andy Shevchenko <andriy.shevchenko@...ux.intel.com>:  
> > > On Thu, Mar 02, 2023 at 09:40:09AM +0100, Henning Schild wrote:  
> > > > Am Wed, 1 Mar 2023 19:28:12 +0200
> > > > schrieb Andy Shevchenko <andriy.shevchenko@...ux.intel.com>:    
> > > > > On Wed, Mar 01, 2023 at 06:02:14PM +0100, Henning Schild
> > > > > wrote:    
> 
> ...
> 
> > > > > > +	.driver = {
> > > > > > +		.name = KBUILD_MODNAME,      
> > > > > 
> > > > > Strictly speaking this is an ABI (as something may
> > > > > instantiate the driver from the user space or elsewhere by
> > > > > this name. At the same time this may change with the file
> > > > > name change.
> > > > > 
> > > > > Personally I prefer explicit string literal here.    
> > > > 
> > > > Switching from one module to three the names have to change.
> > > > People who explicitly loaded the old module which supported
> > > > multiple machines, will now how to load either both oŕ know
> > > > which one to load.    
> > > 
> > > Wait, are you telling that now users load modules _manually_?!  
> > 
> > No i am not, the modules all load automatically. I was trying to
> > construct a hypothetical case where the name change could affect
> > users doing unexpected things.
> >   
> > > > I personally think the ABI change is acceptable, the assumption
> > > > would be that the drivers load automatically anyhow. And since
> > > > there are no params i doubt users will have /etc/modprobe.d/ or
> > > > /sys/module/ stuff around.
> > > > 
> > > > And with the split i guess an ABI change can not be fully
> > > > avoided. Whether the names is explicit or implicit is another
> > > > discussion and just a matter of style. I prefer to stay with
> > > > the currently used pattern, it is not un-common in the kernel.
> > > >   
> > > 
> > > The problem with that pattern is possible, while unlikely,
> > > renaming of the file which triggers this to be updated.
> > > 
> > > Under sysfs the folder will change its name. If user has a script
> > > relying on this, it will be broken. So, I prefer mine.  
> > 
> > Yes, the name of the module will change ... and the location of
> > module metadata and params in sysfs, both not a big deal here.
> > Because there are no params, and there is not need to modprobe
> > manually.  
> 
> It's not only one folder AFAIU. Also folder in the drivers will change
> its name. Parameters is one thing, the folder presence is another.
> 
> Yes, the case is quite unlikely to happen (to break anyone's setup)
> that's why I started this with 'Strictly speaking...'. So, seems you
> are staying on your side, I will leave this to maintainers. If they
> are fine, I will have no objections.

We are splitting one module into three, so we will end up with three
names. Or i miss something here.

The only thing one could talk about is whether that string should be
hardcoded or derived from the name of the c-file.

Anyhow, thanks and we should probably just wait what others have to say.

Henning

> 
> > > > > > +	},      
>