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

Lee Jones
2026-03-26T11:33:41Z

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]