dkms build fails on kernel version >6.8.0

[jschwender]

build fails with error on strlcpy() function.

gcc (Ubuntu 13.2.0-4ubuntu3) 13.2.0

• v4l2loopback version: 0.12.7
• Distribution (+version): _____
  lsb_release -a
  No LSB modules are available.
  Distributor ID: Ubuntu
  Description: Ubuntu 23.10
  Release: 23.10
  Codename: mantic

Steps to reproduce:

build vanilla kernel 6.8.0
run dkms build on installation the kernel

Observed Results:

build fails

Suggested fix:
--- v4l2loopback.c.sav 2023-07-05 14:05:05.000000000 +0200
+++ v4l2loopback.c 2024-03-12 08:36:48.736536585 +0100
@@ -739,7 +739,11 @@
->devicenr;
__u32 capabilities = V4L2_CAP_STREAMING | V4L2_CAP_READWRITE;

+#if LINUX_VERSION_CODE < KERNEL_VERSION(6, 8, 0)
strlcpy(cap->driver, "v4l2 loopback", sizeof(cap->driver));
+#else

• strscpy(cap->driver, "v4l2 loopback", sizeof(cap->driver));
  +#endif
  vidioc_fill_name(cap->card, sizeof(cap->card), devnr);
  snprintf(cap->bus_info, sizeof(cap->bus_info),
  "platform:v4l2loopback-%03d", devnr);
  @@ -1247,7 +1251,11 @@
  if (!cnf)
  BUG();

+#if LINUX_VERSION_CODE < KERNEL_VERSION(6, 8, 0)
strlcpy(q->name, cnf->name, sizeof(q->name));
+#else

• strscpy(q->name, cnf->name, sizeof(q->name));
  +#endif
  q->default_value = cnf->def;
  q->type = cnf->type;
  q->minimum = cnf->min;
  @@ -1352,7 +1360,11 @@
  memset(outp, 0, sizeof(*outp));

  outp->index = index;
  +#if LINUX_VERSION_CODE < KERNEL_VERSION(6, 8, 0)
  strlcpy(outp->name, "loopback in", sizeof(outp->name));
  +#else

• strscpy(outp->name, "loopback in", sizeof(outp->name));
  +#endif
  outp->type = V4L2_OUTPUT_TYPE_ANALOG;
  outp->audioset = 0;
  outp->modulator = 0;
  @@ -1411,7 +1423,11 @@
  memset(inp, 0, sizeof(*inp));

  inp->index = index;
  +#if LINUX_VERSION_CODE < KERNEL_VERSION(6, 8, 0)
  strlcpy(inp->name, "loopback", sizeof(inp->name));
  +#else

• strscpy(inp->name, "loopback", sizeof(inp->name));
  +#endif
  inp->type = V4L2_INPUT_TYPE_CAMERA;
  inp->audioset = 0;
  inp->tuner = 0;

replacing the function for kernels > 6.8 works for me, but i don't feel involved enough with the code, so i want you to look over it and decide if that is a good idea or not. Hope it helps.

[cbricart]

@jschwender fix is already in (yet unreleased) code: first with commit ee177b6 and refined by commit b261f19

[edmundlaugasson]

I can confirm with EndeavourOS:
kernel 6.8.1-arch1-1
v4l2loopback-dkms 0.12.7-2
v4l-utils 1.26.1-1

DKMS make.log for v4l2loopback-0.12.7 for kernel 6.8.1-arch1-1 (x86_64)
Sunday, March 17 2024 10:33:34 EET
Building v4l2-loopback driver...
make -C /usr/lib/modules/6.8.1-arch1-1/build M=/var/lib/dkms/v4l2loopback/0.12.7/build modules
make[1]: Entering directory '/usr/lib/modules/6.8.1-arch1-1/build'
  CC [M]  /var/lib/dkms/v4l2loopback/0.12.7/build/v4l2loopback.o
/var/lib/dkms/v4l2loopback/0.12.7/build/v4l2loopback.c: In function ‘vidioc_querycap’:
/var/lib/dkms/v4l2loopback/0.12.7/build/v4l2loopback.c:717:9: error: implicit declaration of function ‘strlcpy’; did you mean ‘strscpy’? [-Werror=implicit-function-declaration]
  717 |         strlcpy(cap->driver, "v4l2 loopback", sizeof(cap->driver));
      |         ^~~~~~~
      |         strscpy
cc1: some warnings being treated as errors
make[3]: *** [scripts/Makefile.build:243: /var/lib/dkms/v4l2loopback/0.12.7/build/v4l2loopback.o] Error 1
make[2]: *** [/usr/lib/modules/6.8.1-arch1-1/build/Makefile:1921: /var/lib/dkms/v4l2loopback/0.12.7/build] Error 2
make[1]: *** [Makefile:240: __sub-make] Error 2
make[1]: Leaving directory '/usr/lib/modules/6.8.1-arch1-1/build'
make: *** [Makefile:43: v4l2loopback.ko] Error 2

[command-z-z]

I can confirm with EndeavourOS: kernel 6.8.1-arch1-1 v4l2loopback-dkms 0.12.7-2 v4l-utils 1.26.1-1

DKMS make.log for v4l2loopback-0.12.7 for kernel 6.8.1-arch1-1 (x86_64)
Sunday, March 17 2024 10:33:34 EET
Building v4l2-loopback driver...
make -C /usr/lib/modules/6.8.1-arch1-1/build M=/var/lib/dkms/v4l2loopback/0.12.7/build modules
make[1]: Entering directory '/usr/lib/modules/6.8.1-arch1-1/build'
  CC [M]  /var/lib/dkms/v4l2loopback/0.12.7/build/v4l2loopback.o
/var/lib/dkms/v4l2loopback/0.12.7/build/v4l2loopback.c: In function ‘vidioc_querycap’:
/var/lib/dkms/v4l2loopback/0.12.7/build/v4l2loopback.c:717:9: error: implicit declaration of function ‘strlcpy’; did you mean ‘strscpy’? [-Werror=implicit-function-declaration]
  717 |         strlcpy(cap->driver, "v4l2 loopback", sizeof(cap->driver));
      |         ^~~~~~~
      |         strscpy
cc1: some warnings being treated as errors
make[3]: *** [scripts/Makefile.build:243: /var/lib/dkms/v4l2loopback/0.12.7/build/v4l2loopback.o] Error 1
make[2]: *** [/usr/lib/modules/6.8.1-arch1-1/build/Makefile:1921: /var/lib/dkms/v4l2loopback/0.12.7/build] Error 2
make[1]: *** [Makefile:240: __sub-make] Error 2
make[1]: Leaving directory '/usr/lib/modules/6.8.1-arch1-1/build'
make: *** [Makefile:43: v4l2loopback.ko] Error 2

v4l2loopback/0.13.1.r8.gc94a1e8 fix the problem, you can update this package:)