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Date:   Fri, 30 Dec 2022 15:40:41 +0200
From:   Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To:     Ricardo Ribalda <ribalda@chromium.org>
Cc:     Mauro Carvalho Chehab <mchehab@kernel.org>,
        "hn.chen" <hn.chen@sunplusit.com>, linux-media@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH RESEND v2 2/8] media: uvc: Allow quirking by entity guid
Message-ID: <Y67qWROM7rKywU3s@pendragon.ideasonboard.com>
References: <20220920-resend-hwtimestamp-v2-0-0d7978a817cc@chromium.org>
 <20220920-resend-hwtimestamp-v2-2-0d7978a817cc@chromium.org>
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In-Reply-To: <20220920-resend-hwtimestamp-v2-2-0d7978a817cc@chromium.org>
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Hi Ricardo,

Thank you for the patch.


On Fri, Dec 02, 2022 at 06:02:42PM +0100, Ricardo Ribalda wrote:
> When an IP is shared by multiple devices its erratas will be shared by
> all of them. Instead of creating a long list of device quirks, or
> waiting for the users to report errors in their hardware lets add a
> routine to add quirks based on the entity guid.

I'm not thrilled by this. An entity is not an "IP". Quirks are needed to
handle issues with particular firmware versions on particular devices.
The same entity GUID can be used by different devices running different
firmware versions, some that would require a quirk and some that
wouldn't.

> Tested-by: HungNien Chen <hn.chen@sunplusit.com>
> Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> ---
>  drivers/media/usb/uvc/uvc_driver.c | 25 +++++++++++++++++++++++++
>  1 file changed, 25 insertions(+)
> 
> diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
> index 9c05776f11d1..c63ecfd4617d 100644
> --- a/drivers/media/usb/uvc/uvc_driver.c
> +++ b/drivers/media/usb/uvc/uvc_driver.c
> @@ -1493,6 +1493,28 @@ static int uvc_parse_control(struct uvc_device *dev)
>  	return 0;
>  }
>  
> +static const struct uvc_entity_quirk {
> +	u8 guid[16];
> +	u32 quirks;
> +} uvc_entity_quirk[] = {
> +};
> +
> +static void uvc_entity_quirks(struct uvc_device *dev)
> +{
> +	struct uvc_entity *entity;
> +	int i;

unsigned int

> +
> +	list_for_each_entry(entity, &dev->entities, list) {
> +		for (i = 0; i < ARRAY_SIZE(uvc_entity_quirk); i++) {
> +			if (memcmp(entity->guid, uvc_entity_quirk[i].guid,
> +				   sizeof(entity->guid)) == 0) {
> +				dev->quirks |= uvc_entity_quirk[i].quirks;
> +				break;
> +			}
> +		}
> +	}
> +}
> +
>  /* -----------------------------------------------------------------------------
>   * Privacy GPIO
>   */
> @@ -2452,6 +2474,9 @@ static int uvc_probe(struct usb_interface *intf,
>  		goto error;
>  	}
>  
> +	/* Apply entity based quirks */
> +	uvc_entity_quirks(dev);
> +
>  	dev_info(&dev->udev->dev, "Found UVC %u.%02x device %s (%04x:%04x)\n",
>  		 dev->uvc_version >> 8, dev->uvc_version & 0xff,
>  		 udev->product ? udev->product : "<unnamed>",
> 

-- 
Regards,

Laurent Pinchart