[PATCH v5 1/3] lib/igt_sysfs: Add igt_sysfs_get_next_engine

[Kamil Konieczny]

Hi Jonathan,
On 2024-11-07 at 22:52:52 +0000, Jonathan Cavitt wrote:
> Create a new helper function, igt_sysfs_get_next_engine, that iterates
> over sysfs/engines and stores the next engine for the user.  The
> function returns true if the next engine in the list is available, and
> false otherwise.  The function will be used in the test suite in a later
> patch.
> 
> Signed-off-by: Jonathan Cavitt <jonathan.cavitt at intel.com>
> ---
>  lib/igt_sysfs.c | 36 ++++++++++++++++++++++++++++++++++++
>  lib/igt_sysfs.h |  1 +
>  2 files changed, 37 insertions(+)
> 
> diff --git a/lib/igt_sysfs.c b/lib/igt_sysfs.c
> index 26a3aa31fb..3d0dada969 100644
> --- a/lib/igt_sysfs.c
> +++ b/lib/igt_sysfs.c
> @@ -1236,6 +1236,42 @@ static uint16_t xe_get_engine_class(char *name)
>  	return class;
>  }
>  
> +/**
> + * igt_sysfs_get_next_engine:
> + * @engines: fd of the directory engine
> + * @prior: previous engine from the sysfs/engines list
> + *
> + * Iterates over sysfs/engines and stores the next engine in prior.
> + * Returns true if there are more engines to iterate over, and false otherwise.
> + */
> +bool igt_sysfs_get_next_engine(int engines, int *prior)
> +{
> +	struct dirent *de;
> +	DIR *dir;
> +
> +	if (!prior)

This looks buggy, did you mean:
	if (!*prior)

Btw I do not get how it should work, who will close dir?
You could either devise for example iterator:
igt_sysfs_get_first_engine/_next_engine

or for example igt_sysfs_get_egines_names --> return list of engines
names (as seen by 'ls engines') and then iterate over returned list?

List could be na igt_list or something simpler like concatenation of strings
or N * strings\0 + '\0' zero string as end guard?

> +		lseek(engines, 0, SEEK_SET);
> +	else
> +		close(*prior);
> +
> +	dir = fdopendir(engines);

This will open dir at every function call.

Regards,
Kamil

> +	if (!dir) {
> +		close(engines);
> +		return false;
> +	}
> +
> +	while ((de = readdir(dir))) {
> +		if (*de->d_name == '.')
> +			continue;
> +
> +		*prior = openat(engines, de->d_name, O_RDONLY);
> +		if (*prior >= 0)
> +			return true;
> +	}
> +	return false;
> +}
> +
> +
>  /**
>   * igt_sysfs_engines:
>   * @xe: fd of the device
> diff --git a/lib/igt_sysfs.h b/lib/igt_sysfs.h
> index 852b95053f..bff5ed68e6 100644
> --- a/lib/igt_sysfs.h
> +++ b/lib/igt_sysfs.h
> @@ -163,6 +163,7 @@ typedef struct igt_sysfs_rw_attr {
>  
>  void igt_sysfs_rw_attr_verify(igt_sysfs_rw_attr_t *rw);
>  
> +bool igt_sysfs_get_next_engine(int engines, int *prior);
>  void igt_sysfs_engines(int xe, int engines, int gt, bool all, const char **property,
>  		       void (*test)(int, int, const char **, uint16_t, int));
>  
> -- 
> 2.43.0
>