[PATCHv2] iio: iio-mux: use flexible array member

[PATCHv2] iio: iio-mux: use flexible array member

[Rosen Penev]

Make it clear that there's trailing data

Removes a pointer from the struct.

Use array_size for the sizeof calculations. Slightly cleaner.

Signed-off-by: Rosen Penev <rosenp@gmail.com>
---
 v2: use array_size
 drivers/iio/multiplexer/iio-mux.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/iio/multiplexer/iio-mux.c b/drivers/iio/multiplexer/iio-mux.c
index b742ca9a99d1..f2bc8f3aad95 100644
--- a/drivers/iio/multiplexer/iio-mux.c
+++ b/drivers/iio/multiplexer/iio-mux.c
@@ -33,8 +33,8 @@ struct mux {
 	struct iio_channel *parent;
 	struct iio_chan_spec *chan;
 	struct iio_chan_spec_ext_info *ext_info;
-	struct mux_child *child;
 	u32 delay_us;
+	struct mux_child child[];
 };

 static int iio_mux_select(struct mux *mux, int idx)
@@ -381,8 +381,8 @@ static int mux_probe(struct platform_device *pdev)
 	}

 	sizeof_priv = sizeof(*mux);
-	sizeof_priv += sizeof(*mux->child) * children;
-	sizeof_priv += sizeof(*mux->chan) * children;
+	sizeof_priv += array_size(children, sizeof(*mux->child));
+	sizeof_priv += array_size(children, sizeof(*mux->chan));
 	sizeof_priv += sizeof_ext_info;

 	indio_dev = devm_iio_device_alloc(dev, sizeof_priv);
@@ -390,7 +390,6 @@ static int mux_probe(struct platform_device *pdev)
 		return -ENOMEM;

 	mux = iio_priv(indio_dev);
-	mux->child = (struct mux_child *)(mux + 1);
 	mux->chan = (struct iio_chan_spec *)(mux->child + children);

 	platform_set_drvdata(pdev, indio_dev);
--
2.53.0

Re: [PATCHv2] iio: iio-mux: use flexible array member

[Andy Shevchenko]

On Mon, Mar 16, 2026 at 04:29:42PM -0700, Rosen Penev wrote:
> Make it clear that there's trailing data
> 
> Removes a pointer from the struct.
> 
> Use array_size for the sizeof calculations. Slightly cleaner.

array_size()
sizeof()

This commit message is poorly written. Please, consult with
https://chris.beams.io/git-commit on how to write better commit
messages.

...

> struct mux {

>  	struct iio_channel *parent;
>  	struct iio_chan_spec *chan;
>  	struct iio_chan_spec_ext_info *ext_info;
> -	struct mux_child *child;
>  	u32 delay_us;
> +	struct mux_child child[];
>  };

What's the point now to make it VLA? Again, why this and not the other one?

...

>  	mux = iio_priv(indio_dev);
> -	mux->child = (struct mux_child *)(mux + 1);
>  	mux->chan = (struct iio_chan_spec *)(mux->child + children);

(This piece linked to the above comment.)

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCHv2] iio: iio-mux: use flexible array member

[David Lechner]

On 3/17/26 2:26 AM, Andy Shevchenko wrote:
> On Mon, Mar 16, 2026 at 04:29:42PM -0700, Rosen Penev wrote:
>> Make it clear that there's trailing data
>>
>> Removes a pointer from the struct.
>>
>> Use array_size for the sizeof calculations. Slightly cleaner.
> 
> array_size()
> sizeof()
> 
> This commit message is poorly written. Please, consult with
> https://chris.beams.io/git-commit on how to write better commit
> messages.
> 
> ...
> 
>> struct mux {
> 
>>  	struct iio_channel *parent;
>>  	struct iio_chan_spec *chan;
>>  	struct iio_chan_spec_ext_info *ext_info;
>> -	struct mux_child *child;
>>  	u32 delay_us;
>> +	struct mux_child child[];
>>  };
> 
> What's the point now to make it VLA? Again, why this and not the other one?

I agree with Andy here. It doesn't make much sense to use a variable length
array for one when there are other similar arrays in the same struct.


> 
> ...
> 
>>  	mux = iio_priv(indio_dev);
>> -	mux->child = (struct mux_child *)(mux + 1);
>>  	mux->chan = (struct iio_chan_spec *)(mux->child + children);
> 
> (This piece linked to the above comment.)
>