media: uvcvideo: Factor out usb_string() calls

When parsing UVC descriptors to instantiate entity, the driver calls
usb_string() to retrieve the entity name from the device, and falls back
to a default name if the string can't be retrieved. This code pattern
occurs multiple times. Factor it out to a separate helper function.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
---
Ricardo, Guenter, this applies on top of "media: uvcvideo: Handle errors
from calls to usb_string". Any opinion ?
---
 drivers/media/usb/uvc/uvc_driver.c | 59 ++++++++++++++++++------------
 1 file changed, 35 insertions(+), 24 deletions(-)

On 10/25/22 11:47, Laurent Pinchart wrote:
> When parsing UVC descriptors to instantiate entity, the driver calls
> usb_string() to retrieve the entity name from the device, and falls back
> to a default name if the string can't be retrieved. This code pattern
> occurs multiple times. Factor it out to a separate helper function.
> 
> Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> ---
> Ricardo, Guenter, this applies on top of "media: uvcvideo: Handle errors
> from calls to usb_string". Any opinion ?

Great cleanup. Looks good to me.

Reviewed-by: Guenter Roeck <linux@roeck-us.net>

Guenter

> ---
>   drivers/media/usb/uvc/uvc_driver.c | 59 ++++++++++++++++++------------
>   1 file changed, 35 insertions(+), 24 deletions(-)
> 
> diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
> index bd3716a359b0..6eb011f452e5 100644
> --- a/drivers/media/usb/uvc/uvc_driver.c
> +++ b/drivers/media/usb/uvc/uvc_driver.c
> @@ -813,6 +813,27 @@ static struct uvc_entity *uvc_alloc_entity(u16 type, u16 id,
>   	return entity;
>   }
>   
> +static void uvc_entity_set_name(struct uvc_device *dev, struct uvc_entity *entity,
> +				const char *type_name, u8 string_id)
> +{
> +	int ret;
> +
> +	/*
> +	 * First attempt to read the entity name from the device. If the entity
> +	 * has no associated string, or if reading the string fails (most
> +	 * likely due to a buggy firmware), fall back to default names based on
> +	 * the entity type.
> +	 */
> +	if (string_id) {
> +		ret = usb_string(dev->udev, string_id, entity->name,
> +				 sizeof(entity->name));
> +		if (!ret)
> +			return;
> +	}
> +
> +	sprintf(entity->name, "%s %u", type_name, entity->id);
> +}
> +
>   /* Parse vendor-specific extensions. */
>   static int uvc_parse_vendor_control(struct uvc_device *dev,
>   	const unsigned char *buffer, int buflen)
> @@ -879,9 +900,7 @@ static int uvc_parse_vendor_control(struct uvc_device *dev,
>   					       + n;
>   		memcpy(unit->extension.bmControls, &buffer[23+p], 2*n);
>   
> -		if (buffer[24+p+2*n] == 0 ||
> -		    usb_string(udev, buffer[24+p+2*n], unit->name, sizeof(unit->name)) < 0)
> -			sprintf(unit->name, "Extension %u", buffer[3]);
> +		uvc_entity_set_name(dev, unit, "Extension", buffer[24+p+2*n]);
>   
>   		list_add_tail(&unit->list, &dev->entities);
>   		handled = 1;
> @@ -899,6 +918,7 @@ static int uvc_parse_standard_control(struct uvc_device *dev,
>   	struct usb_interface *intf;
>   	struct usb_host_interface *alts = dev->intf->cur_altsetting;
>   	unsigned int i, n, p, len;
> +	const char *type_name;
>   	u16 type;
>   
>   	switch (buffer[2]) {
> @@ -1004,15 +1024,14 @@ static int uvc_parse_standard_control(struct uvc_device *dev,
>   			memcpy(term->media.bmTransportModes, &buffer[10+n], p);
>   		}
>   
> -		if (buffer[7] == 0 ||
> -		    usb_string(udev, buffer[7], term->name, sizeof(term->name)) < 0) {
> -			if (UVC_ENTITY_TYPE(term) == UVC_ITT_CAMERA)
> -				sprintf(term->name, "Camera %u", buffer[3]);
> -			if (UVC_ENTITY_TYPE(term) == UVC_ITT_MEDIA_TRANSPORT_INPUT)
> -				sprintf(term->name, "Media %u", buffer[3]);
> -			else
> -				sprintf(term->name, "Input %u", buffer[3]);
> -		}
> +		if (UVC_ENTITY_TYPE(term) == UVC_ITT_CAMERA)
> +			type_name = "Camera";
> +		else if (UVC_ENTITY_TYPE(term) == UVC_ITT_MEDIA_TRANSPORT_INPUT)
> +			type_name = "Media";
> +		else
> +			type_name = "Input";
> +
> +		uvc_entity_set_name(dev, term, type_name, buffer[7]);
>   
>   		list_add_tail(&term->list, &dev->entities);
>   		break;
> @@ -1045,9 +1064,7 @@ static int uvc_parse_standard_control(struct uvc_device *dev,
>   
>   		memcpy(term->baSourceID, &buffer[7], 1);
>   
> -		if (buffer[8] == 0 ||
> -		    usb_string(udev, buffer[8], term->name, sizeof(term->name)) < 0)
> -			sprintf(term->name, "Output %u", buffer[3]);
> +		uvc_entity_set_name(dev, term, "Output", buffer[8]);
>   
>   		list_add_tail(&term->list, &dev->entities);
>   		break;
> @@ -1068,9 +1085,7 @@ static int uvc_parse_standard_control(struct uvc_device *dev,
>   
>   		memcpy(unit->baSourceID, &buffer[5], p);
>   
> -		if (buffer[5+p] == 0 ||
> -		    usb_string(udev, buffer[5+p], unit->name, sizeof(unit->name)) < 0)
> -			sprintf(unit->name, "Selector %u", buffer[3]);
> +		uvc_entity_set_name(dev, unit, "Selector", buffer[5+p]);
>   
>   		list_add_tail(&unit->list, &dev->entities);
>   		break;
> @@ -1099,9 +1114,7 @@ static int uvc_parse_standard_control(struct uvc_device *dev,
>   		if (dev->uvc_version >= 0x0110)
>   			unit->processing.bmVideoStandards = buffer[9+n];
>   
> -		if (buffer[8+n] == 0 ||
> -		    usb_string(udev, buffer[8+n], unit->name, sizeof(unit->name)) < 0)
> -			sprintf(unit->name, "Processing %u", buffer[3]);
> +		uvc_entity_set_name(dev, unit, "Processing", buffer[8+n]);
>   
>   		list_add_tail(&unit->list, &dev->entities);
>   		break;
> @@ -1128,9 +1141,7 @@ static int uvc_parse_standard_control(struct uvc_device *dev,
>   		unit->extension.bmControls = (u8 *)unit + sizeof(*unit);
>   		memcpy(unit->extension.bmControls, &buffer[23+p], n);
>   
> -		if (buffer[23+p+n] == 0 ||
> -		    usb_string(udev, buffer[23+p+n], unit->name, sizeof(unit->name)) < 0)
> -			sprintf(unit->name, "Extension %u", buffer[3]);
> +		uvc_entity_set_name(dev, unit, "Extension", buffer[23+p+n]);
>   
>   		list_add_tail(&unit->list, &dev->entities);
>   		break;