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Date:   Sun, 20 Dec 2020 18:08:25 +0200
From:   Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To:     Ricardo Ribalda <ribalda@chromium.org>
Cc:     Mauro Carvalho Chehab <mchehab@kernel.org>,
        linux-media@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4 3/9] media: uvcvideo: Allow entities with no pads
Message-ID: <X992+VVFUzOXN5ir@pendragon.ideasonboard.com>
References: <20201215154439.69062-1-ribalda@chromium.org>
 <20201215154439.69062-4-ribalda@chromium.org>
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Hi Ricardo,

Thank you for the patch.

On Tue, Dec 15, 2020 at 04:44:33PM +0100, Ricardo Ribalda wrote:
> Avoid an underflow while calculating the number of inputs for entities
> with zero pads.
> 
> Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> ---
>  drivers/media/usb/uvc/uvc_driver.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
> index 9f4451a2e0a6..534629ecd60d 100644
> --- a/drivers/media/usb/uvc/uvc_driver.c
> +++ b/drivers/media/usb/uvc/uvc_driver.c
> @@ -1033,7 +1033,11 @@ static struct uvc_entity *uvc_alloc_entity(u16 type, u16 id,
>  	unsigned int i;
>  
>  	extra_size = roundup(extra_size, sizeof(*entity->pads));
> -	num_inputs = (type & UVC_TERM_OUTPUT) ? num_pads : num_pads - 1;
> +	if (num_pads)
> +		num_inputs = (type & UVC_TERM_OUTPUT) ? num_pads :
> +								num_pads - 1;

This is a weird indentation. How about the following ?

		num_inputs = type & UVC_TERM_OUTPUT ? num_pads : num_pads - 1;

I can fix this when applying.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

> +	else
> +		num_inputs = 0;
>  	size = sizeof(*entity) + extra_size + sizeof(*entity->pads) * num_pads
>  	     + num_inputs;
>  	entity = kzalloc(size, GFP_KERNEL);
> @@ -1066,7 +1070,7 @@ static struct uvc_entity *uvc_alloc_entity(u16 type, u16 id,
>  
>  	for (i = 0; i < num_inputs; ++i)
>  		entity->pads[i].flags = MEDIA_PAD_FL_SINK;
> -	if (!UVC_ENTITY_IS_OTERM(entity))
> +	if (!UVC_ENTITY_IS_OTERM(entity) && num_pads)
>  		entity->pads[num_pads-1].flags = MEDIA_PAD_FL_SOURCE;
>  
>  	entity->bNrInPins = num_inputs;

-- 
Regards,

Laurent Pinchart