Hi Uwe,

On Thu, Jan 13, 2022 at 11:43 PM Uwe Kleine-König
[off-list ref] wrote:

On Thu, Jan 13, 2022 at 11:57:43PM +0300, Sergey Shtylyov wrote:

quoted

On 1/13/22 11:17 PM, Mark Brown wrote:

quoted

quoted

The subsystems regulator, clk and gpio have the concept of a dummy
resource. For regulator, clk and gpio there is a semantic difference
between the regular _get() function and the _get_optional() variant.
(One might return the dummy resource, the other won't. Unfortunately
which one implements which isn't the same for these three.) The
difference between platform_get_irq() and platform_get_irq_optional() is
only that the former might emit an error message and the later won't.

   This is only a current difference but I'm still going to return 0 ISO
-ENXIO from latform_get_irq_optional(), no way I'd leave that -ENXIO there
alone... :-)

This would address a bit of the critic in my commit log. But as 0 isn't
a dummy value like the dummy values that exist for clk, gpiod and
regulator I still think that the naming is a bad idea because it's not
in the spirit of the other *_get_optional functions.

Seeing you say that -ENXIO is a bad return value for
platform_get_irq_optional() and 0 should be used instead, I wonder why
not changing platform_get_irq() to return 0 instead of -ENXIO, too.
This question is for now only about a sensible semantic. That actually
changing platform_get_irq() is probably harder than changing
platform_get_irq_optional() is a different story.

If only platform_get_irq_optional() is changed and given that the
callers have to do something like:

        if (this_irq_exists()):
                ... (e.g. request_irq)
        else:
                ... (e.g. setup polling)

I really think it's a bad idea that this_irq_exists() has to be
different for platform_get_irq() vs. platform_get_irq_optional().

For platform_get_irq(), the IRQ being absent is an error condition,
hence it should return an error code.
For platform_get_irq_optional(), the IRQ being absent is not an error
condition, hence it should not return an error code, and 0 is OK.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds