i2c: mux: demux-pinctrl: use struct_size() in devm_kzalloc()

One of the more common cases of allocation size calculations is finding the size of a structure that has a zero-sized array at the end, along with memory for some number of elements for that array. For example:

struct foo {
    int stuff;
    void *entry[];
};

instance = devm_kzalloc(dev, sizeof(struct foo) + sizeof(void *) * count, GFP_KERNEL);

Instead of leaving these open-coded and prone to type mistakes, we can now use the new struct_size() helper:

instance = devm_kzalloc(dev, struct_size(instance, entry, count), GFP_KERNEL);

This code was detected with the help of Coccinelle.

---
 drivers/i2c/muxes/i2c-demux-pinctrl.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

index 035032e20327..012b45e447c3 100644
@@ -219,8 +219,8 @@ static int i2c_demux_pinctrl_probe(struct platform_device *pdev)
 		return -EINVAL;
 	}
 
-	priv = devm_kzalloc(&pdev->dev, sizeof(*priv)
-			   + num_chan * sizeof(struct i2c_demux_pinctrl_chan), GFP_KERNEL);
+	priv = devm_kzalloc(&pdev->dev, struct_size(priv, chan, num_chan),
+			    GFP_KERNEL);
 
 	props = devm_kcalloc(&pdev->dev, num_chan, sizeof(*props), GFP_KERNEL);
 

2.20.1

I am okay with this patch in general. However, I think the name of the helper 'struct_size' is a bit unfortunate. I really wondered on the first read why it needs 3 arguments to find out a struct size. I only understood on the second read. I think 'trailing_array_struct_size' would be way more clearer what it does.

I read that as an Acked-by... :-)

Cheers,
Peter

For this patch, yes. Thanks!