Re: regmap I3C support

[Frank Li <Frank.li@nxp.com>]

On Tue, Nov 19, 2024 at 10:41:05AM -0800, Guenter Roeck wrote:
> On 11/19/24 09:46, Mark Brown wrote:
> > On Fri, Nov 15, 2024 at 08:35:04PM -0800, Guenter Roeck wrote:
> > > On 11/14/24 09:26, Mark Brown wrote:
> >
> > > > Right, so the fact that I3C depends on I2C deals with a lot of the
> > > > problems that plague the I2C/SPI combination.  Ugh.  I guess the helper
> > > > should be OK and there's not much doing for I2C/SPI.
> >
> > > It looks like we can use
> >
> > >         if (IS_ENABLED(CONFIG_REGMAP_I3C)) {
> > >                 regmap = devm_regmap_init_i3c(i3cdev, &tmp108_regmap_config);
> > >                 if (IS_ERR(regmap))
> > >                         return dev_err_probe(dev, PTR_ERR(regmap),
> > >                                              "Failed to register i3c regmap\n");
> > > 		...
> > > 	}
> >
> > > even if a stub function is not available as long as there is an external
> > > declaration.
> >
> > > I don't really like it, but it turns out that this kind of code is already used
> > > elsewhere in the kernel. It looks like dead code elimination can now assumed
> > > to be available when building kernel code. We live and learn.
> >
> > Ah, that solves that problem then I guess?
>
>
> Yes. It actually goes a step further - the IS_ENABLED(CONFIG_REGMAP_I3C)) in the
> probe function isn't needed either because the entire i3c probe function is
> optimized away if CONFIG_I3C=n.
>
> I'll send a patch dropping the #ifdef in the tmp108 driver after the commit
> window closes.

Already tried this at v3
https://lore.kernel.org/imx/7bdd2db8-41c8-43d8-ae73-84a221d2d004@roeck-us.net/

but I am not sure if it is good on rely on the compiler. Maybe some option
like some debug option or -O0 cause problem.

Frank

>
> Thanks,
> Guenter
>