Re: [PATCH] platform/x86: panasonic-laptop: simplify allocation of sinf

[Kees Cook <kees@kernel.org>]

On Thu, Mar 19, 2026 at 05:49:28PM -0700, Rosen Penev wrote:
> Change to a flexible array member to allocate once instead of twice.
> 
> Allows using __counted_by for extra runtime analysis. Move the counting
> variable assignment to right after allocation as required by
> __counted_by.
> 
> Remove + 1 to allocation. It's already done in the previous line.

Are you sure this is an accidental +1? I see the "num_sifr++" that
happens earlier, but it's not immediately clear why either that or the
+1 in the original allocation are needed. I'd like to understand why
either/both are/aren't needed.

-Kees

> 
> Signed-off-by: Rosen Penev <rosenp@gmail.com>
> ---
>  drivers/platform/x86/panasonic-laptop.c | 17 ++++-------------
>  1 file changed, 4 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/platform/x86/panasonic-laptop.c b/drivers/platform/x86/panasonic-laptop.c
> index d923ddaa4849..4d663fffbcc8 100644
> --- a/drivers/platform/x86/panasonic-laptop.c
> +++ b/drivers/platform/x86/panasonic-laptop.c
> @@ -248,11 +248,11 @@ struct pcc_acpi {
>  	int			ac_brightness;
>  	int			dc_brightness;
>  	int			current_brightness;
> -	u32			*sinf;
>  	struct acpi_device	*device;
>  	struct input_dev	*input_dev;
>  	struct backlight_device	*backlight;
>  	struct platform_device	*platform;
> +	u32			sinf[] __counted_by(num_sifr);
>  };
>  
>  /*
> @@ -1017,21 +1017,15 @@ static int acpi_pcc_hotkey_add(struct acpi_device *device)
>  	 */
>  	num_sifr++;
>  
> -	pcc = kzalloc_obj(struct pcc_acpi);
> +	pcc = kzalloc_flex(*pcc, sinf, num_sifr);
>  	if (!pcc) {
>  		pr_err("Couldn't allocate mem for pcc");
>  		return -ENOMEM;
>  	}
>  
> -	pcc->sinf = kcalloc(num_sifr + 1, sizeof(u32), GFP_KERNEL);
> -	if (!pcc->sinf) {
> -		result = -ENOMEM;
> -		goto out_hotkey;
> -	}
> -
> +	pcc->num_sifr = num_sifr;
>  	pcc->device = device;
>  	pcc->handle = device->handle;
> -	pcc->num_sifr = num_sifr;
>  	device->driver_data = pcc;
>  	strscpy(acpi_device_name(device), ACPI_PCC_DEVICE_NAME);
>  	strscpy(acpi_device_class(device), ACPI_PCC_CLASS);
> @@ -1039,7 +1033,7 @@ static int acpi_pcc_hotkey_add(struct acpi_device *device)
>  	result = acpi_pcc_init_input(pcc);
>  	if (result) {
>  		pr_err("Error installing keyinput handler\n");
> -		goto out_sinf;
> +		goto out_hotkey;
>  	}
>  
>  	if (!acpi_pcc_retrieve_biosdata(pcc)) {
> @@ -1111,8 +1105,6 @@ static int acpi_pcc_hotkey_add(struct acpi_device *device)
>  	backlight_device_unregister(pcc->backlight);
>  out_input:
>  	input_unregister_device(pcc->input_dev);
> -out_sinf:
> -	kfree(pcc->sinf);
>  out_hotkey:
>  	kfree(pcc);
>  
> @@ -1140,7 +1132,6 @@ static void acpi_pcc_hotkey_remove(struct acpi_device *device)
>  
>  	input_unregister_device(pcc->input_dev);
>  
> -	kfree(pcc->sinf);
>  	kfree(pcc);
>  }
>  
> -- 
> 2.53.0
> 

-- 
Kees Cook