linux-kernel - Re: [PATCH 1/2] drivers: fwnode: fix fwnode_irq_get

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Message-ID: <Y1ennbK6WSHT27Am@paasikivi.fi.intel.com>
Date:   Tue, 25 Oct 2022 09:08:45 +0000
From:   Sakari Ailus <sakari.ailus@...ux.intel.com>
To:     Matti Vaittinen <mazziesaccount@...il.com>
Cc:     Matti Vaittinen <matti.vaittinen@...rohmeurope.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Daniel Scally <djrscally@...il.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Wolfram Sang <wsa@...nel.org>,
        Akhil R <akhilrajeev@...dia.com>, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org
Subject: Re: [PATCH 1/2] drivers: fwnode: fix fwnode_irq_get_byname()

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@...ux.intel.com>
> Signed-off-by: Matti Vaittinen <mazziesaccount@...il.com>
> 
> ---
> 
> 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...

> 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@...ux.intel.com>

> ---
>  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.

> +	if (!ret)
> +		return -EINVAL;
> +
> +	return ret;
>  }
>  EXPORT_SYMBOL(fwnode_irq_get_byname);

-- 
Terveisin,

Sakari Ailus