For the record: all these tests were done with a 3.14-rc5 kernel and sparse
compiled from the git tree as of today (version v0.5.0). The gcc version is 4.8.2.
Regards,
Hans
On 03/15/2014 01:09 PM, Hans Verkuil wrote:
> Hmm, interesting. Twice 'sparse' in the same subject line with different meanings :-)
>
> This is another sparse error I get with drivers/media/v4l2-core/v4l2-ioctl.c:
>
> drivers/media/v4l2-core/v4l2-ioctl.c:424:9: error: cannot size expression
>
> (there are more of those in drivers/media, all with the same cause).
>
> This sparse (the tool) error occurs because of sparse (C language) array initialization
> in combination with ARRAY_SIZE:
>
> static const char *v4l2_memory_names[] = {
> [V4L2_MEMORY_MMAP] = "mmap",
> [V4L2_MEMORY_USERPTR] = "userptr",
> [V4L2_MEMORY_OVERLAY] = "overlay",
> [V4L2_MEMORY_DMABUF] = "dmabuf",
> };
>
> #define prt_names(a, arr) (((unsigned)(a)) < ARRAY_SIZE(arr) ? arr[a] : "unknown")
>
> static void v4l_print_requestbuffers(const void *arg, bool write_only)
> {
> const struct v4l2_requestbuffers *p = arg;
>
> pr_cont("count=%d, type=%s, memory=%s\n",
> p->count,
> prt_names(p->type, v4l2_type_names),
> prt_names(p->memory, v4l2_memory_names));
> }
>
> I could change v4l2_memory_names to:
>
> static const char *v4l2_memory_names[V4L2_MEMORY_DMABUF + 1] = {
>
> and the error goes away.
>
> I'm actually not sure if this is a sparse bug or a feature.
>
> If it is a feature then the error message is definitely wrong, since the size is
> perfectly well defined. As an aside: the error message is pretty vague IMHO.
>
> Regards,
>
> Hans
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