Re: [PATCH 1/2] drivers: fwnode: fix fwnode_irq_get_byname()

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Moro Sakari,

Thanks for the review (and the suggestion)!

On 10/25/22 12:08, Sakari Ailus wrote:
Moi,

On Tue, Oct 25, 2022 at 11:50:59AM +0300, Matti Vaittinen wrote:
The fwnode_irq_get_byname() does return 0 upon device-tree IRQ mapping
failure. This is contradicting the function documentation and can
potentially be a source of errors like:

int probe(...) {
	...

	irq = fwnode_irq_get_byname();
	if (irq <= 0)
		return irq;

	...
}

Here we do correctly check the return value from fwnode_irq_get_byname()
but the driver probe will now return success. (There was already one
such user in-tree).

Change the fwnode_irq_get_byname() to work as documented and according to
the common convention and abd always return a negative errno upon failure.

Fixes: ca0acb511c21 ("device property: Add fwnode_irq_get_byname")
Suggested-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
Signed-off-by: Matti Vaittinen <mazziesaccount@xxxxxxxxx>

---

I did a quick audit for the callers at v6.1-rc2:
drivers/i2c/i2c-smbus.c
drivers/iio/accel/adxl355_core.c
drivers/iio/gyro/fxas21002c_core.c
drivers/iio/imu/adis16480.c
drivers/iio/imu/bmi160/bmi160_core.c
drivers/iio/imu/bmi160/bmi160_core.c

I did not spot any errors to be caused by this change. There will be a

It won't as you're decreasing the possible values the function may
return...


Unless someone had implemented special handling for the IRQ mapping failure...

functional change in i2c-smbus.c as the probe will now return -EINVAL
should the IRQ dt-mapping fail. It'd be nice if this was checked to be
Ok by the peeps knowing the i2c-smbus :)

FWIW, for both patches (but see below):

Reviewed-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>

---
  drivers/base/property.c | 9 +++++++--
  1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/base/property.c b/drivers/base/property.c
index 4d6278a84868..bfc6c7286db2 100644
--- a/drivers/base/property.c
+++ b/drivers/base/property.c
@@ -964,7 +964,7 @@ EXPORT_SYMBOL(fwnode_irq_get);
   */
  int fwnode_irq_get_byname(const struct fwnode_handle *fwnode, const char *name)
  {
-	int index;
+	int index, ret;
if (!name)
  		return -EINVAL;
@@ -973,7 +973,12 @@ int fwnode_irq_get_byname(const struct fwnode_handle *fwnode, const char *name)
  	if (index < 0)
  		return index;
- return fwnode_irq_get(fwnode, index);
+	ret = fwnode_irq_get(fwnode, index);
+

This newline is extra.

Or:

	return ret ?: -EINVAL;

Or even:

	return fwnode_irq_get(fwnode, index) ?: -EINVAL;

Up to you.


My personal preference is to not use the ternary. I think the plain clarity of if() just in many places justifies burning couple of lines more :)

Yours
	-- Matti

--
Matti Vaittinen
Linux kernel developer at ROHM Semiconductors
Oulu Finland

~~ When things go utterly wrong vim users can always type :help! ~~




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