Re: [PATCH 1/3] err.h: add ERR_PTR_CONST macro

Andy Shevchenko
2025-10-30T08:27:43Z

On Wed, Oct 29, 2025 at 04:38:53PM +0100, Christian Marangi wrote:
> On Wed, Oct 29, 2025 at 05:32:48PM +0200, Andy Shevchenko wrote:
> > On Wed, Oct 29, 2025 at 02:33:19PM +0100, Christian Marangi wrote:
> > > Add ERR_PTR_CONST macro to initialize global variables with error
> >
> > ERR_PTR_CONST()
> >
> > > pointers. This might be useful for specific case where there is a global
> > > variables initialized to an error condition and then later set to the
> > > real handle once probe finish/completes.
> >
> > Okay, this has two caveats:
> >
> > 1) naming is bad as it suggests something about const qualifier (and not, it's
> > not about that at all);
> >
> > 2) it doesn't explain what's wrong with ERR_PTR().
> >
>
> It can't be used for global variables as it does cause compilation
> error.

Can you show an example, please?

> I wanted to use ERR_PTR to set the __smem handle instead of freecode
> (void *) -EPROBE_DEFER and notice the compiler doesn't like using
> ERR_PTR().
>
> Then the problem is clear as static declaration require constant value
> for initialization and ERR_PTR is a inline function.
>
> This is why ERR_PTR_CONST following the pattern that was used for
> FIELD_PREP -> FIELD_PREP_CONST that was also introduced for similar
> case.
>
> So yes this is specific for case of static global variables.

--
With Best Regards,
Andy Shevchenko