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 03:57:50PM +0100, Peter Rosin wrote:
> On 2020-03-06 14:58, Andy Shevchenko wrote:
> > 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.
> 
> <rant-mode>
> 
> What do you mean wrong? 

I meant that A is wrong.

> I said that either A or B holds but did not know which
> (with these definitions):
> 
> A. device_get_match_data() digs in the i2c_device_id table and returns the
>    .driver_data of the matching entry.
> B. device_get_match_data() behaves as of_device_get_match_data() and does not
>    dig in the i2c_device_id table, and therefore returns NULL when the driver
>    is probed that way.
> 
> And that in either of these cases your patch made no sense.
> 
> At least that was what I tried to say, using less words...
> 
> And then, according to you, B holds. So, I was right: either A or B holds. BTW,
> I obviously meant the either/or construct to be in the exclusive sense where
> both cannot hold (but my statement is also correct in the inclusive-or sense).
> 
> I would only have been wrong if the correct description had been some third
> option, which I had not mentioned. But that was apparently not the case.

-- 
With Best Regards,
Andy Shevchenko