Hi Uwe, On Wed, Jan 12, 2022 at 9:51 AM Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx> wrote: > On Wed, Jan 12, 2022 at 09:33:48AM +0100, Geert Uytterhoeven wrote: > > On Mon, Jan 10, 2022 at 10:20 PM Andrew Lunn <andrew@xxxxxxx> wrote: > > > On Mon, Jan 10, 2022 at 09:10:14PM +0100, Uwe Kleine-König wrote: > > > > On Mon, Jan 10, 2022 at 10:54:48PM +0300, Sergey Shtylyov wrote: > > > > > This patch is based on the former Andy Shevchenko's patch: > > > > > > > > > > https://lore.kernel.org/lkml/20210331144526.19439-1-andriy.shevchenko@xxxxxxxxxxxxxxx/ > > > > > > > > > > Currently platform_get_irq_optional() returns an error code even if IRQ > > > > > resource simply has not been found. It prevents the callers from being > > > > > error code agnostic in their error handling: > > > > > > > > > > ret = platform_get_irq_optional(...); > > > > > if (ret < 0 && ret != -ENXIO) > > > > > return ret; // respect deferred probe > > > > > if (ret > 0) > > > > > ...we get an IRQ... > > > > > > > > > > All other *_optional() APIs seem to return 0 or NULL in case an optional > > > > > resource is not available. Let's follow this good example, so that the > > > > > callers would look like: > > > > > > > > > > ret = platform_get_irq_optional(...); > > > > > if (ret < 0) > > > > > return ret; > > > > > if (ret > 0) > > > > > ...we get an IRQ... > > > > > > > > The difference to gpiod_get_optional (and most other *_optional) is that > > > > you can use the NULL value as if it were a valid GPIO. > > > > > > > > As this isn't given with for irqs, I don't think changing the return > > > > value has much sense. > > > > > > We actually want platform_get_irq_optional() to look different to all > > > the other _optional() methods because it is not equivalent. If it > > > looks the same, developers will assume it is the same, and get > > > themselves into trouble. > > > > Developers already assume it is the same, and thus forget they have > > to check against -ENXIO instead of zero. > > Is this an ack for renaming platform_get_irq_optional() to > platform_get_irq_silent()? No it isn't ;-) If an optional IRQ is not present, drivers either just ignore it (e.g. for devices that can have multiple interrupts or a single muxed IRQ), or they have to resort to polling. For the latter, fall-back handling is needed elsewhere in the driver. To me it sounds much more logical for the driver to check if an optional irq is non-zero (available) or zero (not available), than to sprinkle around checks for -ENXIO. In addition, you have to remember that this one returns -ENXIO, while other APIs use -ENOENT or -ENOSYS (or some other error code) to indicate absence. I thought not having to care about the actual error code was the main reason behind the introduction of the *_optional() APIs. Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx 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
