Re: [PATCH v2 2/2] IIO: st_accel_i2c.c: Use probe_new() instead of probe()

[Nikolaus Voss]

On Wed, 4 Jul 2018, Andy Shevchenko wrote:
> On Wed, Jul 4, 2018 at 12:09 PM, Nikolaus Voss
> <nikolaus.voss@xxxxxxxxxxxxxxxxxxxxx> wrote:
> > On Wed, 4 Jul 2018, Andy Shevchenko wrote:
> > > On Wed, Jul 4, 2018 at 9:37 AM, Nikolaus Voss
> > > <nikolaus.voss@xxxxxxxxxxxxxxxxxxxxx> wrote:
> > > > On Wed, 4 Jul 2018, Andy Shevchenko wrote:
> > > > > On Tue, Jul 3, 2018 at 9:06 AM, Nikolaus Voss
> > > > > <nikolaus.voss@xxxxxxxxxxxxxxxxxxxxx> wrote:
> > > > > > struct i2c_device_id argument of probe() is not used, so use
> > > > > > probe_new()
> > > > > > instead.
> > > > >
> > > > > This makes...
> > > > >
> > > > > >  MODULE_DEVICE_TABLE(i2c, st_accel_id_table);
> > > > >
> > > > >
> > > > >
> > > > > ...this table obsolete IIUC. At least that's what I did when switched
> > > > > to ->probe_new() in some drivers.
> > > > >
> > > > > If I'm mistaken (again? :-) ) I would hear from someone to point me
> > > > > how it can be used after a switch.
> > > >
> > > >
> > > >
> > > > It is still used by the i2c-core in i2c_device_match() if DT and ACPI
> > > > matching fails.
> > >
> > >
> > > > And it is used to create the corresponding modaliases for
> > > > driver loading.
> > >
> > >
> > > My question is "How?!"
> > > I don't really see any points to match against it after switching to
> > > ->probe_new().
> > >
> > > Could you point me to the code path in i2c (or OF?) core for that?
> >
> >
> > As written above in i2c-core-base.c: i2c_device_match() ->
> > i2c_match_id(driver->id_table,...
> >
> > This is used for driver matching before probe() or probe_new() of the device
> > driver can be called. probe_new() actually is a function signature change
> > only.
>
> Okay, IIUC we got a match. What should we do with it? The table is not
> used in ->probe_new() (in i2c core), so, you can't say which line
> matched there.

The table is not used by the driver, but is necessary to

a) bind an i2c device declared via i2c_board_info with type field set
   to one of the names of the i2c_device_id table to this driver
b) bind an i2c device declared via DT or ACPI but with no match in of_id/
   acpi_id table but an i2c_device_id table match to this driver (fallback
   matching)
c) create the right modaliases at compile time for this driver to make
   module auto-loading work in case of a) and b)

Niko