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SubjectRe: [PATCH 4/5] pci: handled return value of platform_get_irq correctly
On Wed, Mar 18, 2020 at 02:42:48PM +0100, Thomas Gleixner wrote:
> Bjorn Helgaas <helgaas@kernel.org> writes:
> > On Fri, Mar 13, 2020 at 04:56:42PM -0500, Bjorn Helgaas wrote:
> >> On Fri, Mar 13, 2020 at 10:05:58PM +0100, Thomas Gleixner wrote:
> >> > > I think the best pattern is:
> >> > >
> >> > > irq = platform_get_irq(pdev, i);
> >> > > if (irq < 0)
> >> > > return irq;
> >> >
> >> > Careful. 0 is not a valid interrupt.
> >>
> >> Should callers of platform_get_irq() check for a 0 return value?
> >> About 900 of them do not.
>
> I don't know what I was looking at.
>
> platform_get_irq() does the right thing already, so checking for irq < 0
> is sufficient.
>
> Sorry for the confusion!

Thanks, I was indeed confused! Maybe we could reduce future confusion
by strengthening the comments slightly, e.g.,

- * Return: IRQ number on success, negative error number on failure.
+ * Return: non-zero IRQ number on success, negative error number on failure.

I don't want to push my luck, but it's pretty hard to prove that
platform_get_irq() never returns 0. What would you think of something
like the following?

@@ -133,23 +133,24 @@ EXPORT_SYMBOL_GPL(devm_platform_ioremap_resource_byname);
* if (irq < 0)
* return irq;
*
- * Return: IRQ number on success, negative error number on failure.
+ * Return: non-zero IRQ number on success, negative error number on failure.
*/
int platform_get_irq_optional(struct platform_device *dev, unsigned int num)
{
+ int ret;
#ifdef CONFIG_SPARC
/* sparc does not have irqs represented as IORESOURCE_IRQ resources */
if (!dev || num >= dev->archdata.num_irqs)
return -ENXIO;
- return dev->archdata.irqs[num];
+ ret = dev->archdata.irqs[num];
+ goto out;
#else
struct resource *r;
- int ret;

if (IS_ENABLED(CONFIG_OF_IRQ) && dev->dev.of_node) {
ret = of_irq_get(dev->dev.of_node, num);
if (ret > 0 || ret == -EPROBE_DEFER)
- return ret;
+ goto out;
}

r = platform_get_resource(dev, IORESOURCE_IRQ, num);
@@ -157,7 +158,7 @@ int platform_get_irq_optional(struct platform_device *dev, unsigned int num)
if (r && r->flags & IORESOURCE_DISABLED) {
ret = acpi_irq_get(ACPI_HANDLE(&dev->dev), num, r);
if (ret)
- return ret;
+ goto out;
}
}

@@ -171,13 +172,17 @@ int platform_get_irq_optional(struct platform_device *dev, unsigned int num)
struct irq_data *irqd;

irqd = irq_get_irq_data(r->start);
- if (!irqd)
- return -ENXIO;
+ if (!irqd) {
+ ret = -ENXIO;
+ goto out;
+ }
irqd_set_trigger_type(irqd, r->flags & IORESOURCE_BITS);
}

- if (r)
- return r->start;
+ if (r) {
+ ret = r->start;
+ goto out;
+ }

/*
* For the index 0 interrupt, allow falling back to GpioInt
@@ -190,11 +195,14 @@ int platform_get_irq_optional(struct platform_device *dev, unsigned int num)
ret = acpi_dev_gpio_irq_get(ACPI_COMPANION(&dev->dev), num);
/* Our callers expect -ENXIO for missing IRQs. */
if (ret >= 0 || ret == -EPROBE_DEFER)
- return ret;
+ goto out;
}

- return -ENXIO;
+ ret = -ENXIO;
#endif
+out:
+ WARN(ret == 0, "0 is an invalid IRQ number\n");
+ return ret;
}
EXPORT_SYMBOL_GPL(platform_get_irq_optional);

@@ -212,7 +220,7 @@ EXPORT_SYMBOL_GPL(platform_get_irq_optional);
* if (irq < 0)
* return irq;
*
- * Return: IRQ number on success, negative error number on failure.
+ * Return: non-zero IRQ number on success, negative error number on failure.
*/
int platform_get_irq(struct platform_device *dev, unsigned int num)
{
@@ -284,8 +292,10 @@ static int __platform_get_irq_byname(struct platform_device *dev,
}

r = platform_get_resource_byname(dev, IORESOURCE_IRQ, name);
- if (r)
+ if (r) {
+ WARN(r->start == 0, "0 is an invalid IRQ number\n");
return r->start;
+ }

return -ENXIO;
}
@@ -297,7 +307,7 @@ static int __platform_get_irq_byname(struct platform_device *dev,
*
* Get an IRQ like platform_get_irq(), but then by name rather then by index.
*
- * Return: IRQ number on success, negative error number on failure.
+ * Return: non-zero IRQ number on success, negative error number on failure.
*/
int platform_get_irq_byname(struct platform_device *dev, const char *name)
{
@@ -319,7 +329,7 @@ EXPORT_SYMBOL_GPL(platform_get_irq_byname);
* Get an optional IRQ by name like platform_get_irq_byname(). Except that it
* does not print an error message if an IRQ can not be obtained.
*
- * Return: IRQ number on success, negative error number on failure.
+ * Return: non-zero IRQ number on success, negative error number on failure.
*/
int platform_get_irq_byname_optional(struct platform_device *dev,
const char *name)
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