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

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Message-ID: <Y1eGwtqbOhXCGoaM@paasikivi.fi.intel.com>
Date:   Tue, 25 Oct 2022 06:48:34 +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
Subject: Re: [PATCH] drivers: fwnode: fix fwnode_irq_get_byname() kerneldoc

Moi,

On Tue, Oct 25, 2022 at 08:24:24AM +0300, Matti Vaittinen wrote:
> The fwnode_irq_get_byname() may return zero on device-tree mapping
> error. Fix documentation to reflect this as current documentation
> suggests check:
> 
> if (ret < 0)
> is enough to detect the errors. This is not the case.
> 
> Add zero as a return value indicating error.
> 
> Fixes: ca0acb511c21 ("device property: Add fwnode_irq_get_byname")
> Suggested-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> Signed-off-by: Matti Vaittinen <mazziesaccount@...il.com>
> ---
>  drivers/base/property.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/base/property.c b/drivers/base/property.c
> index 4d6278a84868..df437d10aa08 100644
> --- a/drivers/base/property.c
> +++ b/drivers/base/property.c
> @@ -960,7 +960,7 @@ EXPORT_SYMBOL(fwnode_irq_get);
>   * string.
>   *
>   * Return:
> - * Linux IRQ number on success, or negative errno otherwise.
> + * Linux IRQ number on success, zero or negative errno otherwise.

I wonder if it would be possible instead to always return a negative error
code on error. Returning zero on error is really unconventional and can be
expected to be a source of bugs.

We have code already that takes the error code zero into account in e.g.

static int smbalert_probe(struct i2c_client *ara,
                          const struct i2c_device_id *id)
{
...
                irq = fwnode_irq_get_byname(dev_fwnode(adapter->dev.parent),
                                            "smbus_alert");
                if (irq <= 0)
                        return irq;

And zero turns into successful probe!

>   */
>  int fwnode_irq_get_byname(const struct fwnode_handle *fwnode, const char *name)
>  {

-- 
Terveisin,

Sakari Ailus