On Fri, Jan 14, 2022 at 10:58:51AM +0100, Geert Uytterhoeven wrote:
Hi Uwe,
On Thu, Jan 13, 2022 at 11:43 PM Uwe Kleine-König u.kleine-koenig@pengutronix.de wrote:
On Thu, Jan 13, 2022 at 11:57:43PM +0300, Sergey Shtylyov wrote:
On 1/13/22 11:17 PM, Mark Brown wrote:
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.
Please show a few examples how this simplifies the code. If it's only that a driver has to check for == 0 instead of == -ENXIO, than that's not a good enough motivation to make platform_get_irq_optional() different to platform_get_irq().
Best regards Uwe