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

[Kamil Konieczny]

Hi Priyanka,

one more nit, see below.

On 2022-04-26 at 20:34:15 +0530, priyanka.dandamudi at intel.com wrote:
> From: Umesh Nerlige Ramappa <umesh.nerlige.ramappa at intel.com>
> 
> Provide iterators to:
> - construct the subdirectory string for a gt
> - obtain fd for the subdirectory of the interface
> 
> v2: Separated out RPS functionality into seaparate patch (Ashutosh)
> 
> v3: Minute modifications. (Priyanka)
> 
> Cc: Kamil Konieczny <kamil.konieczny at linux.intel.com>
> Cc: Andi Shyti <andi.shyti at intel.com>
> Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> Cc: Sujaritha Sundaresan <sujaritha.sundaresan at intel.com>
> Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa at intel.com>
> Signed-off-by: Ashutosh Dixit <ashutosh.dixit at intel.com>
> Signed-off-by: Priyanka Dandamudi <priyanka.dandamudi at intel.com>
> Reviewed-by: Ashutosh Dixit <ashutosh.dixit at intel.com>
> ---
>  lib/igt_sysfs.c | 71 +++++++++++++++++++++++++++++++++++++++++++++++++
>  lib/igt_sysfs.h | 13 +++++++++
>  2 files changed, 84 insertions(+)
> 
> diff --git a/lib/igt_sysfs.c b/lib/igt_sysfs.c
> index f8ef23e2..4ea93e05 100644
> --- a/lib/igt_sysfs.c
> +++ b/lib/igt_sysfs.c
> @@ -54,6 +54,21 @@
>   * provides basic support for like igt_sysfs_open().
>   */
>  
> +/**
> + * igt_sysfs_has_attr:
> + * @dir: sysfs directory fd
> + * @attr: attr inside sysfs dir that needs to be checked for existence
> + *
> + * This checks if specified attr exists in device sysfs directory.
> + *
> + * Returns:
> + * true if attr exists in sysfs, false otherwise.
> + */
> +bool igt_sysfs_has_attr(int dir, const char *attr)
> +{
> +	return !faccessat(dir, attr, F_OK, 0);
> +}
> +
>  /**
>   * igt_sysfs_path:
>   * @device: fd of the device
> @@ -104,6 +119,62 @@ int igt_sysfs_open(int device)
>  	return open(path, O_RDONLY);
>  }
>  
> +/**
> + * igt_sysfs_gt_path:
> + * @device: fd of the device
> + * @gt: gt number
> + * @path: buffer to fill with the sysfs gt path to the device
> + * @pathlen: length of @path buffer
> + *
> + * This finds the sysfs directory corresponding to @device and @gt. If the gt
> + * specific directory is not available and gt is 0, path is filled with sysfs
> + * base directory.
> + *
> + * Returns:
> + * The directory path, or NULL on failure.
> + */
> +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 (!access(path, F_OK))
> +		return path;
> +	else if (!gt)
> +		return igt_sysfs_path(device, path, pathlen);
> +
> +	return NULL;
> +}
> +
> +/**
> + * igt_sysfs_gt_open:
> + * @device: fd of the device
> + * @gt: gt number
> + *
> + * This opens the sysfs gt directory corresponding to device and gt for use
> + * with igt_sysfs_set() and igt_sysfs_get().
> + *
> + * Returns:
> + * The directory fd, or -1 on failure.
> + */
> +int igt_sysfs_gt_open(int device, int gt)
> +{
> +	char path[96];
> +
> +	if (igt_debug_on(!igt_sysfs_gt_path(device, gt, path, sizeof(path))))
----------- ^
imho here we should not use igt_debug_on because we use this
function in iterator macro for_each_sysfs_gt_dirfd and the end
condition is hitting end of available GTs and returning -1.

Regards,
Kamil

> +		return -1;
> +
> +	return open(path, O_RDONLY);
> +}
> +
>  /**
>   * igt_sysfs_write:
>   * @dir: directory for the device from igt_sysfs_open()
> diff --git a/lib/igt_sysfs.h b/lib/igt_sysfs.h
> index 56741a0a..33317a96 100644
> --- a/lib/igt_sysfs.h
> +++ b/lib/igt_sysfs.h
> @@ -28,8 +28,21 @@
>  #include <stdbool.h>
>  #include <stdarg.h>
>  
> +#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__++)
> +
>  char *igt_sysfs_path(int device, char *path, int pathlen);
>  int igt_sysfs_open(int device);
> +char *igt_sysfs_gt_path(int device, int gt, char *path, int pathlen);
> +int igt_sysfs_gt_open(int device, int gt);
> +bool igt_sysfs_has_attr(int dir, const char *attr);
>  
>  int igt_sysfs_read(int dir, const char *attr, void *data, int len);
>  int igt_sysfs_write(int dir, const char *attr, const void *data, int len);
> -- 
> 2.25.1
>