Thanks for catching that and sorry for the delayed response, I was on vacation. I think your analysis makes sense. I would personally lean towards the former suggestion (keeping the change localized to the return value of platform_get_irq() which is the function that apparently has an informal contract about returning -ENXIO specifically). I am happy to post a PATCH v3 to that effect if this seems amenable. Thanks Enrico Granata | egranata@xxxxxxxxxx | ChromeOS | MTV1600 On Wed, Feb 20, 2019 at 10:05 AM Brian Norris <briannorris@xxxxxxxxxxxx> wrote: > > Hi, > > On Mon, Feb 11, 2019 at 11:01:12AM -0800, egranata@xxxxxxxxxxxx wrote: > > From: Enrico Granata <egranata@xxxxxxxxxxxx> > > > > ACPI 5 added support for GpioInt resources as a way to provide > > information about interrupts mediated via a GPIO controller. > > > > Several device buses (e.g. SPI, I2C) have support for retrieving > > an IRQ specified via this type of resource, and providing it > > directly to the driver as an IRQ number. > > > > This is not currently done for the platform drivers, as platform_get_irq() > > does not try to parse GpioInt() resources. This requires drivers to > > either have to support only one possible IRQ resource, or to have code > > in place to try both as a failsafe. > > > > While there is a possibility of ambiguity for devices that exposes > > multiple IRQs, it is easy and feasible to support the common case > > of devices that only expose one IRQ which would be of either type > > depending on the underlying system's architecture. > > > > This commit adds support for parsing a GpioInt resource in order > > to fulfill a request for the index 0 IRQ for a platform device. > > > > Signed-off-by: Enrico Granata <egranata@xxxxxxxxxxxx> > > --- > > Changes in v2: > > - only support IRQ index 0 > > > > drivers/base/platform.c | 15 ++++++++++++++- > > 1 file changed, 14 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/base/platform.c b/drivers/base/platform.c > > index 1c958eb33ef4d..0d3611cd1b3bc 100644 > > --- a/drivers/base/platform.c > > +++ b/drivers/base/platform.c > > @@ -127,7 +127,20 @@ int platform_get_irq(struct platform_device *dev, unsigned int num) > > irqd_set_trigger_type(irqd, r->flags & IORESOURCE_BITS); > > } > > > > - return r ? r->start : -ENXIO; > > + if (r) > > + return r->start; > > + > > + /* > > + * For the index 0 interrupt, allow falling back to GpioInt > > + * resources. While a device could have both Interrupt and GpioInt > > + * resources, making this fallback ambiguous, in many common cases > > + * the device will only expose one IRQ, and this fallback > > + * allows a common code path across either kind of resource. > > + */ > > + if (num == 0 && has_acpi_companion(&dev->dev)) > > + return acpi_dev_gpio_irq_get(ACPI_COMPANION(&dev->dev), num); > > For ACPI devices, this changes the return code for a missing interrupt > 0 from ENXIO to ENOENT, because acpi_dev_gpio_irq_get() uses ENOENT > instead of ENXIO. While ENXIO isn't exactly documented as the *specific* > error code for a missing interrupt in platform_get_irq(), there are > definitely drivers out there that are looking specifically for ENXIO > (grepping the tree finds several Rockchip platform drivers and a few > ethernet drivers at a minimum). And it also incidentally broke some > usage of the very driver you were trying to support > (drivers/platform/chrome/cros_ec_lpc.c). > > I suspect a good strategy here would be to check > acpi_dev_gpio_irq_get()'s return codes here with something like: > > if (ret > 0 || ret == -EPROBE_DEFER) > return ret; > return -ENXIO; > > Although, the gpiolib functions embedded in there also can return EIO, > so maybe something like this is better? > > if (ret == -ENOENT || ret == 0) > return -ENXIO; > return ret; > > I'm kinda unsure what to do with error codes besides PROBE_DEFER or > "missing", since most users don't really have it in their mind that > platform_get_irq() can fail with EIO or similar. > > Brian > > > + > > + return -ENXIO; > > #endif > > } > > EXPORT_SYMBOL_GPL(platform_get_irq); > > -- > > 2.20.1.791.gb4d0f1c61a-goog > >
