On Wed, Jan 12, 2022 at 02:38:37PM +0100, Andrew Lunn wrote: > > 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. > > The *_optional() functions return an error code if there has been a > real error which should be reported up the call stack. This excludes > whatever error code indicates the requested resource does not exist, > which can be -ENODEV etc. If the device does not exist, a magic cookie > is returned which appears to be a valid resources but in fact is > not. So the users of these functions just need to check for an error > code, and fail the probe if present. > > You seems to be suggesting in binary return value: non-zero > (available) or zero (not available) No, what is suggested is to (besides the API changes): - do not treat ENXIO as something special in platform_get_irq*() - allow platform_get_irq*() to return other error codes > This discards the error code when something goes wrong. That is useful > information to have, so we should not be discarding it. > > IRQ don't currently have a magic cookie value. One option would be to > add such a magic cookie to the subsystem. Otherwise, since 0 is > invalid, return 0 to indicate the IRQ does not exist. > > The request for a script checking this then makes sense. However, i > don't know how well coccinelle/sparse can track values across function > calls. They probably can check for: > > ret = irq_get_optional() > if (ret < 0) > return ret; > > A missing if < 0 statement somewhere later is very likely to be an > error. A comparison of <= 0 is also likely to be an error. A check for > > 0 before calling any other IRQ functions would be good. I'm > surprised such a check does not already existing in the IRQ API, but > there are probably historical reasons for that. > > Andrew -- With Best Regards, Andy Shevchenko
