[v2,2/2] i2c: i2c-smbus: fwnode_irq_get_byname() return value fix

Commit Message

Matti Vaittinen Oct. 25, 2022, 3:12 p.m. UTC

The fwnode_irq_get_byname() was changed to not return 0 upon failure so
return value check can be adjusted to reflect the change.

Signed-off-by: Matti Vaittinen <[e-mail]>
Reviewed-by: Sakari Ailus <[e-mail]>
Reviewed-by: Andy Shevchenko <[e-mail]>

---

Depends on the mentioned return value change which is in patch 1/2. The
return value change does also cause a functional change here. Eg. when
IRQ mapping fails, the fwnode_irq_get_byname() no longer returns zero.
This will cause also the probe here to return nonzero failure. I guess
this is desired behaviour.
---
 drivers/i2c/i2c-smbus.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Andy Shevchenko Oct. 25, 2022, 4:30 p.m. UTC | #1

On Tue, Oct 25, 2022 at 06:12:11PM +0300, Matti Vaittinen wrote:
> The fwnode_irq_get_byname() was changed to not return 0 upon failure so
> return value check can be adjusted to reflect the change.

...

> Depends on the mentioned return value change which is in patch 1/2. The
> return value change does also cause a functional change here. Eg. when
> IRQ mapping fails, the fwnode_irq_get_byname() no longer returns zero.
> This will cause also the probe here to return nonzero failure. I guess
> this is desired behaviour.

The entire error handling there looks suspicious.

The 'struct i2c_smbus_alert_setup' description says:

 "If irq is not specified, the smbus_alert driver doesn't take care of
  interrupt handling. In that case it is up to the I2C bus driver to
  either handle the interrupts or to poll for alerts."

So, the question is, shouldn't we just drop the check completely?

Vaittinen, Matti Oct. 27, 2022, 5:40 a.m. UTC | #2

On 10/25/22 19:30, Andy Shevchenko wrote:
> On Tue, Oct 25, 2022 at 06:12:11PM +0300, Matti Vaittinen wrote:
>> The fwnode_irq_get_byname() was changed to not return 0 upon failure so
>> return value check can be adjusted to reflect the change.
> 
> ...
> 
>> Depends on the mentioned return value change which is in patch 1/2. The
>> return value change does also cause a functional change here. Eg. when
>> IRQ mapping fails, the fwnode_irq_get_byname() no longer returns zero.
>> This will cause also the probe here to return nonzero failure. I guess
>> this is desired behaviour.
> 
> The entire error handling there looks suspicious.
> 
> The 'struct i2c_smbus_alert_setup' description says:
> 
>   "If irq is not specified, the smbus_alert driver doesn't take care of
>    interrupt handling. In that case it is up to the I2C bus driver to
>    either handle the interrupts or to poll for alerts."
> 
> So, the question is, shouldn't we just drop the check completely?

I don't really know what this means. Does it mean that if IRQ is not 
provided, the driver needs to take care of alerts (in which case the 
check here is very valid because IRQ is required for smbus_alert 
driver). Or does it mean that only the IRQ handling is omitted while the 
smbus_alert driver should do all the other stuff (what ever that is) as 
usual. In this case this check indeed feels wrong.

I would appreciate someone with more insight to this driver to take a 
look at it.

Yours
	-- Matti

Vaittinen, Matti Nov. 15, 2022, 9:09 a.m. UTC | #3

On 10/27/22 08:40, Matti Vaittinen wrote:
> On 10/25/22 19:30, Andy Shevchenko wrote:
>> On Tue, Oct 25, 2022 at 06:12:11PM +0300, Matti Vaittinen wrote:
>>> The fwnode_irq_get_byname() was changed to not return 0 upon failure so
>>> return value check can be adjusted to reflect the change.
>>
>> ...
>>
>>> Depends on the mentioned return value change which is in patch 1/2. The
>>> return value change does also cause a functional change here. Eg. when
>>> IRQ mapping fails, the fwnode_irq_get_byname() no longer returns zero.
>>> This will cause also the probe here to return nonzero failure. I guess
>>> this is desired behaviour.
>>
>> The entire error handling there looks suspicious.
>>
>> The 'struct i2c_smbus_alert_setup' description says:
>>
>>   "If irq is not specified, the smbus_alert driver doesn't take care of
>>    interrupt handling. In that case it is up to the I2C bus driver to
>>    either handle the interrupts or to poll for alerts."
>>
>> So, the question is, shouldn't we just drop the check completely?
> 
> I don't really know what this means. Does it mean that if IRQ is not 
> provided, the driver needs to take care of alerts (in which case the 
> check here is very valid because IRQ is required for smbus_alert 
> driver). Or does it mean that only the IRQ handling is omitted while the 
> smbus_alert driver should do all the other stuff (what ever that is) as 
> usual. In this case this check indeed feels wrong.
> 
> I would appreciate someone with more insight to this driver to take a 
> look at it.

Wolfram, do you have the required insight?

What would be the best way to proceed? I see 3 options:

1. fix the return value as is done by this series.
https://lore.kernel.org/all/[e-mail]/
	=> Will cause the i2c-smbus probe to return failure also if IRQ
	   mapping fails.

2. apply the 1/1 from the series "as is" - but drop the return value 
check for fwnode_irq_get_byname() altogether as was suggested by Andy

3. drop this series and apply the documentation fix suggested in:
https://lore.kernel.org/all/[e-mail]/

Thoughts anyone?

Yours
	-- Matti

Patch

diff --git a/drivers/i2c/i2c-smbus.c b/drivers/i2c/i2c-smbus.c
index 07c92c8495a3..d0cc4b7903ed 100644
--- a/drivers/i2c/i2c-smbus.c
+++ b/drivers/i2c/i2c-smbus.c
@@ -130,7 +130,7 @@  static int smbalert_probe(struct i2c_client *ara,
 	} else {
 		irq = fwnode_irq_get_byname(dev_fwnode(adapter->dev.parent),
 					    "smbus_alert");
-		if (irq <= 0)
+		if (irq < 0)
 			return irq;
 	}