[PATCH i-g-t 2/5] lib/igt_configfs: Add helper to mount configfs

[Kamil Konieczny]

Hi Riana,
On 2025-04-22 at 15:25:58 +0530, Riana Tauro wrote:
> From: José Expósito <jose.exposito89 at gmail.com>
> 
> Add a new helper function to mount and open configfs
> 
> Co-developed-by: Jim Shargo <jshargo at chromium.org>
> Signed-off-by: Jim Shargo <jshargo at chromium.org>
> Co-developed-by: Marius Vlad <marius.vlad at collabora.com>
> Signed-off-by: Marius Vlad <marius.vlad at collabora.com>
> Co-developed-by: Riana Tauro <riana.tauro at intel.com>
> Signed-off-by: Riana Tauro <riana.tauro at intel.com>
> Signed-off-by: José Expósito <jose.exposito89 at gmail.com>
> ---
>  lib/igt.h          |  1 +
>  lib/igt_configfs.c | 82 ++++++++++++++++++++++++++++++++++++++++++++++
>  lib/igt_configfs.h | 15 +++++++++
>  lib/meson.build    |  1 +
>  4 files changed, 99 insertions(+)
>  create mode 100644 lib/igt_configfs.c
>  create mode 100644 lib/igt_configfs.h
> 
> diff --git a/lib/igt.h b/lib/igt.h
> index 58c39e098..173ca70bf 100644
> --- a/lib/igt.h
> +++ b/lib/igt.h
> @@ -27,6 +27,7 @@
>  #include "drmtest.h"
>  #include "i915_3d.h"
>  #include "igt_aux.h"
> +#include "igt_configfs.h"
>  #include "igt_core.h"
>  #include "igt_debugfs.h"
>  #include "igt_draw.h"
> diff --git a/lib/igt_configfs.c b/lib/igt_configfs.c
> new file mode 100644
> index 000000000..6b202b76f
> --- /dev/null
> +++ b/lib/igt_configfs.c
> @@ -0,0 +1,82 @@
> +// SPDX-License-Identifier: MIT
> +/*
> + * Copyright © 2023 Google LLC.
> + * Copyright © 2023 Collabora, Ltd.
> + * Copyright © 2024 Red Hat, Inc.
> + * Copyright © 2025 Intel Corporation
> + */
> +
> +#include <sys/mount.h>

sys/mount.h should be after limits.h

> +#include <fcntl.h>
> +#include <limits.h>
> +
> +#include "igt_aux.h"
> +#include "igt_configfs.h"
> +
> +/**
> + * SECTION:igt_configfs
> + * @short_description: Support code for configfs features
> + * @title: configfs
> + * @include: igt_configfs.h
> + *
> + * This library provides helpers to access configfs features.
> + */
> +
> +/*
> + * General configfs helpers
> + */
> +
> +static const char *__igt_configfs_mount(void)
> +{
> +	if (igt_is_mountpoint("/sys/kernel/config"))
> +		return "/sys/kernel/config";
> +
> +	if (igt_is_mountpoint("/config"))
> +		return "/config";
> +
> +	if (mount("config", "/sys/kernel/config", "configfs", 0, 0))
> +		return NULL;
> +
> +	return "/sys/kernel/config";
> +}
> +
> +/**
> + * igt_configfs_mount:
> + *
> + * This attempts to locate where configfs is mounted on the filesystem,
> + * and if not found, will then try to mount configfs at /sys/kernel/config.
> + *
> + * Returns:
> + * The path to the configfs mount point (e.g. /sys/kernel/config)
> + */
> +const char *igt_configfs_mount(void)
> +{
> +	static const char *path;
> +
> +	if (!path)
> +		path = __igt_configfs_mount();
> +
> +	return path;
> +}
> +
> +/**
> + * igt_configfs_open: open configfs path
> + * @name: name of the configfs directory
> + *
> + * Opens the configfs directory corresponding to the name
> + *
> + * Returns:
> + * The directory fd, or -1 on failure.
> + */
> +int igt_configfs_open(const char *name)
> +{
> +	char path[PATH_MAX];
> +	const char *configfs_path;
> +
> +	configfs_path = igt_configfs_mount();
> +	igt_assert(configfs_path);

Try to not using asserts in libs, rather return -1 here,
you could add igt_debug if you think it will help here, so

	if (!configfs_path) {
		igt_debug("configfs not mounted, errno=%d\n", errno);

		return -1;
	}

Regards,
Kamil

> +
> +	snprintf(path, sizeof(path), "%s/%s", configfs_path, name);
> +
> +	return open(path, O_RDONLY);
> +}
> diff --git a/lib/igt_configfs.h b/lib/igt_configfs.h
> new file mode 100644
> index 000000000..91f95659b
> --- /dev/null
> +++ b/lib/igt_configfs.h
> @@ -0,0 +1,15 @@
> +/* SPDX-License-Identifier: MIT */
> +/*
> + * Copyright © 2023 Google LLC.
> + * Copyright © 2023 Collabora, Ltd.
> + * Copyright © 2024 Red Hat, Inc.
> + * Copyright © 2025 Intel Corporation
> + */
> +
> +#ifndef __IGT_CONFIGFS_H__
> +#define __IGT_CONFIGFS_H__
> +
> +const char *igt_configfs_mount(void);
> +int igt_configfs_open(const char *name);
> +
> +#endif /* __IGT_CONFIGFS_H__ */
> diff --git a/lib/meson.build b/lib/meson.build
> index 8517cd540..59072d8ce 100644
> --- a/lib/meson.build
> +++ b/lib/meson.build
> @@ -18,6 +18,7 @@ lib_sources = [
>  	'i915/i915_crc.c',
>  	'igt_collection.c',
>  	'igt_color_encoding.c',
> +	'igt_configfs.c',
>  	'igt_facts.c',
>  	'igt_crc.c',
>  	'igt_debugfs.c',
> -- 
> 2.47.1
>