Re: [PATCH v1 1/9] pinctrl: mcp23s08: Get rid of legacy platform data

[Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>]

On Wed, Sep 22, 2021 at 09:36:21AM +0300, Andy Shevchenko wrote:
> On Thu, Sep 16, 2021 at 02:51:23PM +0200, Florian Eckert wrote:
> > Hello Andy,
> > 
> > I just wanted to port my target an APU3 (x86_64) to kernel version 5.10 in
> > OpenWrt.
> > This is the next stable LTS kernel version in OpenWrt.
> > 
> > On my board I have this device as an I2c bus IO-expander with which I
> > control additional LEDs.
> > For this purpose I have a platform driver. Which registers these additional
> > LEDs.
> > I have now discovered that the platform driver no longer compiles due to
> > this change, as the platform data for the mcp23017 have been removed by this
> > change in kernel version 5.8.

Ah, now I got it. You want to instantiate the I2C expander itself, so as I
mentioned below it can be easily done via SSDT overlays:

https://connect.linaro.org/resources/lvc21f/lvc21f-304/
https://www.youtube.com/watch?v=nlKjUAv3RL0&ab_channel=OSDNConf

https://stackoverflow.com/questions/65727454/
https://stackoverflow.com/questions/60105101/
https://stackoverflow.com/questions/54768841/
https://stackoverflow.com/questions/46095840/

https://github.com/westeri/meta-acpi/tree/master/recipes-bsp/acpi-tables/samples/

> > I don't have control over the BIOS (coreboot)
> 
> It's open source.
> 
> > and I can't adjust the ACPI
> > tables.
> 
> Actually you can (to some extend) even for closed sourced firmwares (either
> with rewriting DSDT as Hackintosh project does, or via SSDT overlays, I gave a
> talk on Linaro Connect about this).
> 
> > Since this is an x86 platform, I can't work with a device tree, can I?
> 
> Ideally you need to fix the ACPI tables, but this won't fix older firmwares
> anyway. As a workaround you may convert platform data to use software nodes.
> 
> See the example (in v5.15-rc1):
> 
> 	drivers/mfd/intel_quark_i2c_gpio.c
> 	drivers/gpio/gpio-dwapb.c
> 	drivers/i2c/busses/i2c-designware-platdrv.c
> 
> of such conversion.
> 
> > On 2020-04-07 19:38, Andy Shevchenko wrote:
> > > Platform data is a legacy interface to supply device properties
> > > to the driver. In this case we even don't have in-kernel users
> > > for it. Just remove it for good.

-- 
With Best Regards,
Andy Shevchenko