Both drmIoctl and ioctl define second argument as unigned long, but DRM_IOCTL do not.
Debugging/tracing tools (like strace or valgrind) on 64-bit machines see different request value for ioctls with 32nd bit set, because casting signed int to unsigned long extends 32nd bit to upper word, so 0x80000000 becomes 0xFFFFFFFF80000000)
Nobody noticed because higher 32 bits are chopped off on their way to kernel. --- xf86drmMode.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/xf86drmMode.c b/xf86drmMode.c index 0d268fc..f08e648 100644 --- a/xf86drmMode.c +++ b/xf86drmMode.c @@ -52,7 +52,7 @@ #define U642VOID(x) ((void *)(unsigned long)(x)) #define VOID2U64(x) ((uint64_t)(unsigned long)(x))
-static inline DRM_IOCTL(int fd, int cmd, void *arg) +static inline int DRM_IOCTL(int fd, unsigned long cmd, void *arg) { int ret = drmIoctl(fd, cmd, arg); return ret < 0 ? -errno : ret;