Re: [PATCH 1/2] i2c: i801: Switch to iomapped register access

[Heiner Kallweit <hkallweit1@gmail.com>]

On 19.03.2025 00:22, Andi Shyti wrote:
> Hi Andy,
> 
> On Wed, Mar 19, 2025 at 12:18:47AM +0200, Andy Shevchenko wrote:
>> Wed, Mar 12, 2025 at 08:07:23PM +0100, Heiner Kallweit kirjoitti:
>>> Switch to iomapped register access as a prerequisite for adding
>>> support for MMIO register access.
>>
>> I believe that I at least discussed the similar change a few years ago or even
>> proposed a one. The problem here is that *_p() variants of IO port accessors
>> are not the same as non-_p ones. And commit message is kept silent about
>> possible consequences of this change.
>>
>> So, at bare minumum it would be good to test for some period of time before
>> going for it.
> 
> How would you do it?
> 

Documentation/driver-api/device-io.rst states that the artificially delayed
_p versions were needed on ISA devices. And in general I didn't find any hint
that the non-delayed versions ever caused issues on PCI devices.
On my system using the non-delayed version works fine, but I can't say 100%
that it's the same for the very first (> 25 yrs ago) chipsets supported by i801.

Likely users with old systems don't run -next kernels, therefore leaving
this change a full cycle in -next may not really help. We can argue that
we have the -rc period for testing (and reverting if needed).

> Andi

Heiner