[PATCH] media: em28xx: fix inverted tuner capability check for VBI device

[PATCH] media: em28xx: fix inverted tuner capability check for VBI device

[Christopher Snowhill]

Commit 8e53399c63c3 ("media: em28xx: Add support for Empia em2828X
bridge") changed the condition for setting V4L2_CAP_TUNER on the VBI
device from "dev->tuner_type != TUNER_ABSENT" to a check of the video
device's capabilities, but inverted it: the VBI node now advertises a
tuner only when the video node does not have one.

On boards without a tuner (e.g. the MyGica iGrabber, card=105) the VBI
device's device_caps therefore contain V4L2_CAP_TUNER, while the shared
vidioc_querycap() correctly omits it from cap->capabilities. This trips
the sanity check in v4l_querycap() whenever the VBI node is queried,
for example by udev's v4l_id on every hotplug:

  WARNING: drivers/media/v4l2-core/v4l2-ioctl.c:1119 at v4l_querycap+0xff/0x110 [videodev]
  (cap->capabilities & (vfd->device_caps | V4L2_CAP_DEVICE_CAPS)) != (vfd->device_caps | V4L2_CAP_DEVICE_CAPS)

It also leaves the tuner ioctls enabled on the VBI node of tuner-less
boards and disables them on boards that do have a tuner.

Restore the intended logic so the VBI device has V4L2_CAP_TUNER exactly
when the video device does.

Fixes: 8e53399c63c3 ("media: em28xx: Add support for Empia em2828X bridge")
Assisted-by: LLM
Signed-off-by: Christopher Snowhill <chris@kode54.net>
Cc: stable@vger.kernel.org
---
 drivers/media/usb/em28xx/em28xx-video.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/media/usb/em28xx/em28xx-video.c b/drivers/media/usb/em28xx/em28xx-video.c
index c418add65bb5..cdf1dc692b08 100644
--- a/drivers/media/usb/em28xx/em28xx-video.c
+++ b/drivers/media/usb/em28xx/em28xx-video.c
@@ -3001,7 +3001,7 @@ static int em28xx_v4l2_init(struct em28xx *dev)
 		v4l2->vbi_dev.queue->lock = &v4l2->vb_vbi_queue_lock;
 		v4l2->vbi_dev.device_caps = V4L2_CAP_STREAMING |
 			V4L2_CAP_READWRITE | V4L2_CAP_VBI_CAPTURE;
-		if ((v4l2->vdev.device_caps & V4L2_CAP_TUNER) == 0)
+		if (v4l2->vdev.device_caps & V4L2_CAP_TUNER)
 			v4l2->vbi_dev.device_caps |= V4L2_CAP_TUNER;
 
 		/* disable inapplicable ioctls */
-- 
2.55.0