v4l2loopback-dc is incompatible with Linux 6.15+

[Jamim]

Describe the bug
Due to removal of some functions in Linux 6.15, v4l2loopback-dc build fails.

Expected behavior
v4l2loopback-dc builds successfully with Linux kernel 6.15+.

Additional context
I use Gentoo Linux, so here is my emerge droidcam log:
droidcam-2.1.3:20250529-070836.log

[amfern]

this suppose to address it #292

[Jamim]

Hello @amfern,

Thanks for your effort! 🙇🏼
Unfortunately, it looks like that PR fixes only one of missing functions.

click to see all the errors

v4l2loopback-dc.c: In function ‘buffer_written’:
v4l2loopback-dc.c:1514:3: error: implicit declaration of function ‘del_timer_sync’ [-Wimplicit-function-declaration]
 1514 |   del_timer_sync(&dev->sustain_timer);
      |   ^~~~~~~~~~~~~~
v4l2loopback-dc.c: At top level:
v4l2loopback-dc.c:2347:4: error: ‘const struct v4l2_ioctl_ops’ has no member named ‘vidioc_queryctrl’; did you mean ‘vidioc_querycap’?
 2347 |   .vidioc_queryctrl         = &vidioc_queryctrl,
      |    ^~~~~~~~~~~~~~~~
      |    vidioc_querycap
v4l2loopback-dc.c:2347:31: error: initialization of ‘int (*)(struct file *, void *, struct v4l2_dv_timings *)’ from incompatible pointer type ‘int (*)(struct fi
le *, void *, struct v4l2_queryctrl *)’ [-Wincompatible-pointer-types]
 2347 |   .vidioc_queryctrl         = &vidioc_queryctrl,
      |                               ^
v4l2loopback-dc.c:2347:31: note: (near initialization for ‘v4l2_loopback_ioctl_ops.vidioc_s_dv_timings’)
v4l2loopback-dc.c:1151:1: note: ‘vidioc_queryctrl’ declared here
 1151 | vidioc_queryctrl(struct file *file, void *fh,
      | ^~~~~~~~~~~~~~~~
v4l2loopback-dc.c:2348:4: error: ‘const struct v4l2_ioctl_ops’ has no member named ‘vidioc_g_ctrl’; did you mean ‘vidioc_g_std’?
 2348 |   .vidioc_g_ctrl            = &vidioc_g_ctrl,
      |    ^~~~~~~~~~~~~
      |    vidioc_g_std
v4l2loopback-dc.c:2348:31: error: initialization of ‘int (*)(struct file *, void *, struct v4l2_dv_timings *)’ from incompatible pointer type ‘int (*)(struct file *, void *, struct v4l2_control *)’ [-Wincompatible-pointer-types]
 2348 |   .vidioc_g_ctrl            = &vidioc_g_ctrl,
      |                               ^
v4l2loopback-dc.c:2348:31: note: (near initialization for ‘v4l2_loopback_ioctl_ops.vidioc_g_dv_timings’)
v4l2loopback-dc.c:1200:1: note: ‘vidioc_g_ctrl’ declared here
 1200 | vidioc_g_ctrl(struct file *file, void *fh,
      | ^~~~~~~~~~~~~
v4l2loopback-dc.c:2349:4: error: ‘const struct v4l2_ioctl_ops’ has no member named ‘vidioc_s_ctrl’; did you mean ‘vidioc_s_std’?
 2349 |   .vidioc_s_ctrl            = &vidioc_s_ctrl,
      |    ^~~~~~~~~~~~~
      |    vidioc_s_std
v4l2loopback-dc.c:2349:31: error: initialization of ‘int (*)(struct file *, void *, struct v4l2_dv_timings *)’ from incompatible pointer type ‘int (*)(struct file *, void *, struct v4l2_control *)’ [-Wincompatible-pointer-types]
 2349 |   .vidioc_s_ctrl            = &vidioc_s_ctrl,
      |                               ^
v4l2loopback-dc.c:2349:31: note: (near initialization for ‘v4l2_loopback_ioctl_ops.vidioc_query_dv_timings’)
v4l2loopback-dc.c:1227:1: note: ‘vidioc_s_ctrl’ declared here
 1227 | vidioc_s_ctrl(struct file *file, void *fh,
      | ^~~~~~~~~~~~~

[amfern]

Hi @Jamim

I updated the PR and tested that the driver works on arch distro, can you check again?

[Jamim]

Hi @Jamim

I updated the PR and tested that the driver works on test distro, can you check again?

Now it builds and works fine on Linux 6.15 🎉
Thank you, @amfern!