[igt-dev] [PATCH i-g-t 2/6] lib/igt_sysfs: Add helpers to iterate over GTs

[Dixit, Ashutosh]

On Thu, 21 Apr 2022 07:52:07 -0700, <priyanka.dandamudi at intel.com> wrote:
>
> +char *igt_sysfs_gt_path(int device, int gt, char *path, int pathlen)
> +{
> +	struct stat st;
> +
> +	if (device < 0)
> +		return NULL;
> +
> +	if (igt_debug_on(fstat(device, &st)) || igt_debug_on(!S_ISCHR(st.st_mode)))
> +		return NULL;
> +
> +	snprintf(path, pathlen, "/sys/dev/char/%d:%d/gt/gt%d",
> +		 major(st.st_rdev), minor(st.st_rdev), gt);
> +
> +	if (!igt_debug_on(access(path, F_OK)))
> +		return path;
> +	else if (!igt_debug_on(gt != 0))
> +		return igt_sysfs_path(device, path, pathlen);

I think these two igt_debug_on()'s should be removed. The issue is the
for_each_sysfs_gt() loops below will send a gt value 1 greater than the
actual number of gt's (at which point this function returns NULL and the
loops exit). And then these igt_debug_on's will fire during the normal
course of operation whereas they are meant to fire only in error. So if we
fix this, this code becomes:

> +	if (!(access(path, F_OK)))
> +		return path;
> +	else if (!gt)
> +		return igt_sysfs_path(device, path, pathlen);

The rest LGTM, so with that fixed, this is:

Reviewed-by: Ashutosh Dixit <ashutosh.dixit at intel.com>

> +#define for_each_sysfs_gt_path(i915__, path__, pathlen__) \
> +	for (int gt__ = 0; \
> +	     igt_sysfs_gt_path(i915__, gt__, path__, pathlen__) != NULL; \
> +	     gt__++)
> +
> +#define for_each_sysfs_gt_dirfd(i915__, dirfd__, gt__) \
> +	for (gt__ = 0; \
> +	     (dirfd__ = igt_sysfs_gt_open(i915__, gt__)) != -1; \
> +	     close(dirfd__), gt__++)