Re: [PATCH v1 2/5] i2c: mux: pca954x: Make use of device properties

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Fri, Mar 06, 2020 at 12:48:14PM +0100, Peter Rosin wrote:
> On 2020-03-06 10:54, Andy Shevchenko wrote:
> > On Thu, Mar 05, 2020 at 09:05:56PM +0000, Peter Rosin wrote:
> >> On 2020-03-05 16:53, Andy Shevchenko wrote:
> >>> Device property API allows to gather device resources from different sources,
> >>> such as ACPI. Convert the drivers to unleash the power of device property API.
> > 
> > ...
> > 
> >>>  static const struct i2c_device_id pca954x_id[] = {
> >>> -	{ "pca9540", pca_9540 },
> >>> -	{ "pca9542", pca_9542 },
> >>> -	{ "pca9543", pca_9543 },
> >>> -	{ "pca9544", pca_9544 },
> >>> -	{ "pca9545", pca_9545 },
> >>> -	{ "pca9546", pca_9546 },
> >>> -	{ "pca9547", pca_9547 },
> >>> -	{ "pca9548", pca_9548 },
> >>> -	{ "pca9846", pca_9846 },
> >>> -	{ "pca9847", pca_9847 },
> >>> -	{ "pca9848", pca_9848 },
> >>> -	{ "pca9849", pca_9849 },
> >>> +	{ "pca9540", .driver_data = (kernel_ulong_t)&chips[pca_9540] },
> >>> +	{ "pca9542", .driver_data = (kernel_ulong_t)&chips[pca_9542] },
> >>> +	{ "pca9543", .driver_data = (kernel_ulong_t)&chips[pca_9543] },
> >>> +	{ "pca9544", .driver_data = (kernel_ulong_t)&chips[pca_9544] },
> >>> +	{ "pca9545", .driver_data = (kernel_ulong_t)&chips[pca_9545] },
> >>> +	{ "pca9546", .driver_data = (kernel_ulong_t)&chips[pca_9546] },
> >>> +	{ "pca9547", .driver_data = (kernel_ulong_t)&chips[pca_9547] },
> >>> +	{ "pca9548", .driver_data = (kernel_ulong_t)&chips[pca_9548] },
> >>> +	{ "pca9846", .driver_data = (kernel_ulong_t)&chips[pca_9846] },
> >>> +	{ "pca9847", .driver_data = (kernel_ulong_t)&chips[pca_9847] },
> >>> +	{ "pca9848", .driver_data = (kernel_ulong_t)&chips[pca_9848] },
> >>> +	{ "pca9849", .driver_data = (kernel_ulong_t)&chips[pca_9849] },
> >>
> >> It feels odd/wrong to specifically name .driver_data when .name is not there.
> >> None or both...
> > 
> > I will add .name as well.
> > 
> >>> +	data->chip = device_get_match_data(dev);
> >>>  	if (!data->chip)
> >>>  		data->chip = &chips[id->driver_data];
> >>
> >> These two lines no longer make any sence.
> > 
> > Please elaborate.
> > 
> > IIRC Javier explained once that I²C ID table is still good to have to allow
> > enumeration from user space.
> 
> id->driver_data is no longer an integer index into chips[]. So, for the I2C
> ID table case, either device_get_match_data returns the .driver_data as-is
> from the pca954x_id array, or it returns NULL (I don't know which it is).

No, you took it wrong. device_get_match_data() operates with ACPI/DT tables.

> In the first case, if (!data->chip) ...; is useless dead code. In the latter
> case, it should be
> 
> 	if (!data->chip)
> 		data->chip = (whatever-type-chip-is *)id->driver_data;
> 
> (If it's this latter case, I get the feeling that changing the .driver_data
> of pca954x_id is an orthogonal change that has little to do with using
> device properties instead of of-specifics.)

But this comment is good, seems I missed that and actually change is not needed
indeed.

-- 
With Best Regards,
Andy Shevchenko