On Fri, 10 Jun 2022 10:45:33 +0200
Nuno Sá <nuno.sa@xxxxxxxxxx> wrote:
> APIs like of_iio_channel_get_by_name() and of_iio_channel_get_all() were
> returning a mix of NULL and error pointers being NULL the way to
pointers with NULL being the way to...
> "notify" that we should do a "system" lookup for channels. This make
> it very confusing and prone to errors as commit dbbccf7c20bf
> ("iio: inkern: fix return value in devm_of_iio_channel_get_by_name()")
> proves. On top of this, patterns like 'if (channel != NULL) return channel'
> were being used where channel could actually be an error code which
> makes the code hard to read.
>
> Signed-off-by: Nuno Sá <nuno.sa@xxxxxxxxxx>
> ---
> drivers/iio/inkern.c | 24 +++++++++++-------------
> 1 file changed, 11 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/iio/inkern.c b/drivers/iio/inkern.c
> index 87fd2a0d44f2..31d9c122199a 100644
> --- a/drivers/iio/inkern.c
> +++ b/drivers/iio/inkern.c
> @@ -214,7 +214,7 @@ static struct iio_channel *of_iio_channel_get(struct device_node *np, int index)
> struct iio_channel *of_iio_channel_get_by_name(struct device_node *np,
> const char *name)
> {
> - struct iio_channel *chan = NULL;
> + struct iio_channel *chan;
>
> /* Walk up the tree of devices looking for a matching iio channel */
> while (np) {
> @@ -231,11 +231,11 @@ struct iio_channel *of_iio_channel_get_by_name(struct device_node *np,
> name);
> chan = of_iio_channel_get(np, index);
> if (!IS_ERR(chan) || PTR_ERR(chan) == -EPROBE_DEFER)
> - break;
This original behaviour is 'interesting'. If we get a error like -ENOMEM
we should return it rather than carry on. Do we have enough knowledge
of possible errors here to be more explicit on when we keep looking up
the tree? I think we can get -ENOENT from of_parse_phandle_with_args()
That raises an interesting question on whether -ENODEV is the right response
for the previously NULL case or is -ENOENT more consistent with other
of_ functions? No device could be thought of as being the case that needs
to defer (in hope it turns up later) whereas no entry means it will never
succeed.
> - else if (name && index >= 0) {
> + return chan;
> + if (name && index >= 0) {
> pr_err("ERROR: could not get IIO channel %pOF:%s(%i)\n",
> np, name ? name : "", index);
> - return NULL;
> + return chan;
> }
>
> /*
> @@ -245,10 +245,10 @@ struct iio_channel *of_iio_channel_get_by_name(struct device_node *np,
> */
> np = np->parent;
> if (np && !of_get_property(np, "io-channel-ranges", NULL))
> - return NULL;
> + return chan;
> }
>
> - return chan;
> + return ERR_PTR(-ENODEV);
> }
> EXPORT_SYMBOL_GPL(of_iio_channel_get_by_name);
>
> @@ -267,8 +267,8 @@ static struct iio_channel *of_iio_channel_get_all(struct device *dev)
> break;
> } while (++nummaps);
>
> - if (nummaps == 0) /* no error, return NULL to search map table */
> - return NULL;
> + if (nummaps == 0) /* return -ENODEV to search map table */
> + return ERR_PTR(-ENODEV);
>
> /* NULL terminated array to save passing size */
> chans = kcalloc(nummaps + 1, sizeof(*chans), GFP_KERNEL);
> @@ -295,7 +295,7 @@ static struct iio_channel *of_iio_channel_get_all(struct device *dev)
>
> static inline struct iio_channel *of_iio_channel_get_all(struct device *dev)
> {
> - return NULL;
> + return ERR_PTR(-ENODEV);
> }
>
> #endif /* CONFIG_OF */
> @@ -362,7 +362,7 @@ struct iio_channel *iio_channel_get(struct device *dev,
> if (dev) {
> channel = of_iio_channel_get_by_name(dev->of_node,
> channel_name);
> - if (channel != NULL)
> + if (!IS_ERR(channel) || PTR_ERR(channel) == -EPROBE_DEFER)
> return channel;
> }
>
> @@ -412,8 +412,6 @@ struct iio_channel *devm_of_iio_channel_get_by_name(struct device *dev,
> channel = of_iio_channel_get_by_name(np, channel_name);
> if (IS_ERR(channel))
> return channel;
> - if (!channel)
> - return ERR_PTR(-ENODEV);
>
> ret = devm_add_action_or_reset(dev, devm_iio_channel_free, channel);
> if (ret)
> @@ -436,7 +434,7 @@ struct iio_channel *iio_channel_get_all(struct device *dev)
> return ERR_PTR(-EINVAL);
>
> chans = of_iio_channel_get_all(dev);
> - if (chans)
> + if (!IS_ERR(chans) || PTR_ERR(chans) == -EPROBE_DEFER)
Hmm. We only want to carry on if the error is -ENODEV. Anything else
should be reported up the stack.
That might be the only error left, but I think we should be explicit.
> return chans;
>
> name = dev_name(dev);
