[PATCH v2 0/2] media: uvcvideo: Fix Fix deferred probing error

[PATCH v2 0/2] media: uvcvideo: Fix Fix deferred probing error

[Ricardo Ribalda]

uvc_gpio_parse() can return -EPROBE_DEFER when the GPIOs it depends on
have not yet been probed.

Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
---
Changes in v2:
- Add follow-up patch for using dev_err_probe
- Avoid error_retcode style
- Link to v1: https://lore.kernel.org/r/20250129-uvc-eprobedefer-v1-1-643b2603c0d2@chromium.org

---
Ricardo Ribalda (2):
      media: uvcvideo: Fix deferred probing error
      media: uvcvideo: Use dev_err_probe for devm_gpiod_get_optional

 drivers/media/usb/uvc/uvc_driver.c | 36 ++++++++++++++++++++++++++----------
 1 file changed, 26 insertions(+), 10 deletions(-)
---
base-commit: f4b211714bcc70effa60c34d9fa613d182e3ef1e
change-id: 20250129-uvc-eprobedefer-b5ebb4db63cc

Best regards,
-- 
Ricardo Ribalda <ribalda@chromium.org>

[PATCH v2 1/2] media: uvcvideo: Fix deferred probing error

[Ricardo Ribalda]

uvc_gpio_parse() can return -EPROBE_DEFER when the GPIOs it depends on
have not yet been probed. This return code should be propagated to the
caller of uvc_probe() to ensure that probing is retried when the required
GPIOs become available.

Currently, this error code is incorrectly converted to -ENODEV,
causing some internal cameras to be ignored.

This commit fixes this issue by propagating the -EPROBE_DEFER error.

Cc: stable@vger.kernel.org
Fixes: 2886477ff987 ("media: uvcvideo: Implement UVC_EXT_GPIO_UNIT")
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
---
 drivers/media/usb/uvc/uvc_driver.c | 27 +++++++++++++++++++--------
 1 file changed, 19 insertions(+), 8 deletions(-)

diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
index deadbcea5e22..e966bdb9239f 100644
--- a/drivers/media/usb/uvc/uvc_driver.c
+++ b/drivers/media/usb/uvc/uvc_driver.c
@@ -2231,13 +2231,16 @@ static int uvc_probe(struct usb_interface *intf,
 #endif
 
 	/* Parse the Video Class control descriptor. */
-	if (uvc_parse_control(dev) < 0) {
+	ret = uvc_parse_control(dev);
+	if (ret < 0) {
+		ret = -ENODEV;
 		uvc_dbg(dev, PROBE, "Unable to parse UVC descriptors\n");
 		goto error;
 	}
 
 	/* Parse the associated GPIOs. */
-	if (uvc_gpio_parse(dev) < 0) {
+	ret = uvc_gpio_parse(dev);
+	if (ret < 0) {
 		uvc_dbg(dev, PROBE, "Unable to parse UVC GPIOs\n");
 		goto error;
 	}
@@ -2263,24 +2266,32 @@ static int uvc_probe(struct usb_interface *intf,
 	}
 
 	/* Register the V4L2 device. */
-	if (v4l2_device_register(&intf->dev, &dev->vdev) < 0)
+	ret = v4l2_device_register(&intf->dev, &dev->vdev);
+	if (ret < 0)
 		goto error;
 
 	/* Scan the device for video chains. */
-	if (uvc_scan_device(dev) < 0)
+	if (uvc_scan_device(dev) < 0) {
+		ret = -ENODEV;
 		goto error;
+	}
 
 	/* Initialize controls. */
-	if (uvc_ctrl_init_device(dev) < 0)
+	if (uvc_ctrl_init_device(dev) < 0) {
+		ret = -ENODEV;
 		goto error;
+	}
 
 	/* Register video device nodes. */
-	if (uvc_register_chains(dev) < 0)
+	if (uvc_register_chains(dev) < 0) {
+		ret = -ENODEV;
 		goto error;
+	}
 
 #ifdef CONFIG_MEDIA_CONTROLLER
 	/* Register the media device node */
-	if (media_device_register(&dev->mdev) < 0)
+	ret = media_device_register(&dev->mdev);
+	if (ret < 0)
 		goto error;
 #endif
 	/* Save our data pointer in the interface data. */
@@ -2314,7 +2325,7 @@ static int uvc_probe(struct usb_interface *intf,
 error:
 	uvc_unregister_video(dev);
 	kref_put(&dev->ref, uvc_delete);
-	return -ENODEV;
+	return ret;
 }
 
 static void uvc_disconnect(struct usb_interface *intf)

-- 
2.48.1.711.g2feabab25a-goog

[PATCH v2 2/2] media: uvcvideo: Use dev_err_probe for devm_gpiod_get_optional

[Ricardo Ribalda]

Use the dev_err_probe() helper for devm_gpiod_get_optional(), like we do
with gpiod_to_irq()

That eventually calls device_set_deferred_probe_reason() which can be
helpful for tracking down problems.

Suggested-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
---
 drivers/media/usb/uvc/uvc_driver.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
index e966bdb9239f..0094cfc092d6 100644
--- a/drivers/media/usb/uvc/uvc_driver.c
+++ b/drivers/media/usb/uvc/uvc_driver.c
@@ -1297,8 +1297,13 @@ static int uvc_gpio_parse(struct uvc_device *dev)
 
 	gpio_privacy = devm_gpiod_get_optional(&dev->intf->dev, "privacy",
 					       GPIOD_IN);
-	if (IS_ERR_OR_NULL(gpio_privacy))
-		return PTR_ERR_OR_ZERO(gpio_privacy);
+	if (!gpio_privacy)
+		return 0;
+
+	if (IS_ERR(gpio_privacy))
+		return dev_err_probe(&dev->intf->dev,
+				     PTR_ERR(gpio_privacy),
+				     "Can't get privacy GPIO\n");
 
 	irq = gpiod_to_irq(gpio_privacy);
 	if (irq < 0)

-- 
2.48.1.711.g2feabab25a-goog

Re: [PATCH v2 2/2] media: uvcvideo: Use dev_err_probe for devm_gpiod_get_optional

[Doug Anderson]

Hi,

On Mon, Mar 3, 2025 at 11:07 AM Ricardo Ribalda <ribalda@chromium.org> wrote:
>
> Use the dev_err_probe() helper for devm_gpiod_get_optional(), like we do
> with gpiod_to_irq()
>
> That eventually calls device_set_deferred_probe_reason() which can be
> helpful for tracking down problems.
>
> Suggested-by: Doug Anderson <dianders@chromium.org>
> Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> ---
>  drivers/media/usb/uvc/uvc_driver.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)

Reviewed-by: Douglas Anderson <dianders@chromium.org>

NOTE: If it were up to me, I would have also changed the caller of
uvc_gpio_parse() to no longer print an error message in the case of
errors. After your patch here all causes of errors in uvc_gpio_parse()
will have already printed something, so the extra print is not
terribly useful and just clutters the code and logs. That being said,
it's not a huge deal and I'm happy to let owners of this code indicate
what they like. :-)

-Doug