linux-kernel - Re: [PATCH v1 1/2] platform/x86/intel: Introduce Intel Elkhart Lake PSE I/O

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Message-ID: <aQSJJv7d2hllsObY@smile.fi.intel.com>
Date: Fri, 31 Oct 2025 12:02:14 +0200
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Raag Jadav <raag.jadav@...el.com>
Cc: hansg@...nel.org, ilpo.jarvinen@...ux.intel.com,
	linus.walleij@...aro.org, brgl@...ev.pl,
	platform-driver-x86@...r.kernel.org, linux-gpio@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/2] platform/x86/intel: Introduce Intel Elkhart Lake
 PSE I/O

On Fri, Oct 31, 2025 at 10:34:28AM +0100, Raag Jadav wrote:
> On Wed, Oct 29, 2025 at 10:36:19AM +0200, Andy Shevchenko wrote:
> > On Wed, Oct 29, 2025 at 11:50:49AM +0530, Raag Jadav wrote:

...

> > > +#define EHL_PSE_IO_DEV_OFFSET	SZ_4K
> > > +#define EHL_PSE_IO_DEV_SIZE	SZ_4K
> > 
> > Not sure if SZ_4K is a good idea for the _OFFSET, the _SIZE is fine. Also why
> > do we need two? If the devices are of the same size, we don't need to have a
> > separate offset.
> 
> Yes but they're semantically different, atleast as per DEFINE_RES_MEM().
> Either way works for me.

They are "slices" in the HW, see also my "if the devices..." passage.

If you want to use SZ_* in _OFFSET, I would write it as (1 * SZ_4K) to point
out that size constant here is the _unit_ and not the size semantically.
Currently the definitions have the same values semantically, but you pointed
out that they should not be.

...

> > > +	io_dev = kzalloc(sizeof(*io_dev), GFP_KERNEL);
> > > +	if (!io_dev)
> > > +		return -ENOMEM;
> > 
> > Why devm_kzalloc() can't be used? I don't see if the device lifetime is anyhow
> > different to this object. Am I wrong?
> 
> Looks like it but I don't know the code well enough to tell if there're
> corner cases, so just following the documented rules. Your call.

Do you expect this to be called in non-probe() contexts? If no --> devm.
Otherwise some comments are needed.

...

> > > +	ret = __auxiliary_device_add(aux_dev, dev->driver->name);
> > 
> > Hmm... Is it okay to use double underscored variant? Only a single driver uses
> > this so far... Care to elaborate?
> 
> The regular variant uses KBUILD_MODNAME which comes with 'intel' prefix
> after commit df7f9acd8646, and with that we overshoot the max id string
> length for leaf drivers.

At bare minimum this needs a comment, but I think ideally we need to bump the
limit by factor of 2.

> > > +	if (ret)
> > > +		goto uninit_aux_dev;

-- 
With Best Regards,
Andy Shevchenko