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

[Andy Shevchenko]

On Thu, Oct 30, 2025 at 10:27:38AM +0200, Andy Shevchenko wrote:
> 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?

Ah, it's probably due to static inline...

> > 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