Re: [PATCH] leds: pca955x: kzalloc + kcalloc to single kzalloc

[Lee Jones <lee@kernel.org>]

On Thu, 19 Mar 2026, Rosen Penev wrote:

> Two fewer allocations as a result.
> 
> Required placing some structs before others as flexible array members
> require a complete definition. Declaration is not enough.
> 
> Added __counted_by support for one of the structs for extra runtime
> analysis.
> 
> Signed-off-by: Rosen Penev <rosenp@gmail.com>
> ---
>  drivers/leds/leds-pca955x.c | 45 ++++++++++++++-----------------------
>  1 file changed, 17 insertions(+), 28 deletions(-)
> 
> diff --git a/drivers/leds/leds-pca955x.c b/drivers/leds/leds-pca955x.c
> index 2007fe6217ec..ee5f02eaa3c9 100644
> --- a/drivers/leds/leds-pca955x.c
> +++ b/drivers/leds/leds-pca955x.c
> @@ -112,19 +112,6 @@ static const struct pca955x_chipdef pca955x_chipdefs[] = {
>  	},
>  };
>  
> -struct pca955x {
> -	struct mutex lock;
> -	struct pca955x_led *leds;
> -	const struct pca955x_chipdef	*chipdef;
> -	struct i2c_client	*client;
> -	unsigned long active_blink;
> -	unsigned long active_pins;
> -	unsigned long blink_period;
> -#ifdef CONFIG_LEDS_PCA955X_GPIO
> -	struct gpio_chip gpio;
> -#endif
> -};
> -
>  struct pca955x_led {
>  	struct pca955x	*pca955x;
>  	struct led_classdev	led_cdev;
> @@ -137,8 +124,21 @@ struct pca955x_led {
>  #define led_to_pca955x(l)	container_of(l, struct pca955x_led, led_cdev)
>  
>  struct pca955x_platform_data {
> -	struct pca955x_led	*leds;
>  	int			num_leds;
> +	struct pca955x_led	leds[] __counted_by(num_leds);

Where is the memory allocated to this now?

Why do we need this in both structs?

> +};
> +
> +struct pca955x {
> +	struct mutex lock;
> +	const struct pca955x_chipdef	*chipdef;
> +	struct i2c_client	*client;
> +	unsigned long active_blink;
> +	unsigned long active_pins;
> +	unsigned long blink_period;
> +#ifdef CONFIG_LEDS_PCA955X_GPIO
> +	struct gpio_chip gpio;
> +#endif
> +	struct pca955x_led leds[];
>  };
>  
>  /* 8 bits per input register */
> @@ -542,15 +542,11 @@ pca955x_get_pdata(struct i2c_client *client, const struct pca955x_chipdef *chip)
>  	if (count > chip->bits)
>  		return ERR_PTR(-ENODEV);
>  
> -	pdata = devm_kzalloc(&client->dev, sizeof(*pdata), GFP_KERNEL);
> +	pdata = devm_kzalloc(&client->dev, struct_size(pdata, leds, chip->bits), GFP_KERNEL);
>  	if (!pdata)
>  		return ERR_PTR(-ENOMEM);
>  
> -	pdata->leds = devm_kcalloc(&client->dev,
> -				   chip->bits, sizeof(struct pca955x_led),
> -				   GFP_KERNEL);
> -	if (!pdata->leds)
> -		return ERR_PTR(-ENOMEM);
> +	pdata->num_leds = chip->bits;
>  
>  	device_for_each_child_node(&client->dev, child) {
>  		u32 reg;
> @@ -568,8 +564,6 @@ pca955x_get_pdata(struct i2c_client *client, const struct pca955x_chipdef *chip)
>  		fwnode_property_read_u32(child, "type", &led->type);
>  	}
>  
> -	pdata->num_leds = chip->bits;
> -
>  	return pdata;
>  }
>  
> @@ -623,15 +617,10 @@ static int pca955x_probe(struct i2c_client *client)
>  		return -ENODEV;
>  	}
>  
> -	pca955x = devm_kzalloc(&client->dev, sizeof(*pca955x), GFP_KERNEL);
> +	pca955x = devm_kzalloc(&client->dev, struct_size(pca955x, leds, chip->bits), GFP_KERNEL);
>  	if (!pca955x)
>  		return -ENOMEM;
>  
> -	pca955x->leds = devm_kcalloc(&client->dev, chip->bits,
> -				     sizeof(*pca955x_led), GFP_KERNEL);
> -	if (!pca955x->leds)
> -		return -ENOMEM;
> -
>  	i2c_set_clientdata(client, pca955x);
>  
>  	mutex_init(&pca955x->lock);
> -- 
> 2.53.0
> 

-- 
Lee Jones [李琼斯]