[igt-dev] [PATCH i-g-t 2/6] lib/debugfs: Function to read debugfs with the directory already open

[Souza, Jose]

On Wed, 2018-08-29 at 14:57 -0700, Dhinakaran Pandiyan wrote:
> tests/kms_frontbuffer_tracking and tests/kms_psr read debugfs nodes
> several times after opening the directory once. There is already an
> implementation of this in the kms_frontbuffer_tracking, moving that
> functionality to the library will allow us to share the code with
> kms_psr
> and kms_fbcon_fbt
> 

Reviewed-by: José Roberto de Souza <jose.souza at intel.com>

> Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan at intel.com>
> ---
>  lib/igt_debugfs.c                | 39
> ++++++++++++++++++++++++++++++---------
>  lib/igt_debugfs.h                |  3 ++-
>  tests/kms_frontbuffer_tracking.c |  7 ++-----
>  3 files changed, 34 insertions(+), 15 deletions(-)
> 
> diff --git a/lib/igt_debugfs.c b/lib/igt_debugfs.c
> index 14753a9e..baedc225 100644
> --- a/lib/igt_debugfs.c
> +++ b/lib/igt_debugfs.c
> @@ -262,26 +262,47 @@ int igt_debugfs_open(int device, const char
> *filename, int mode)
>  	return ret;
>  }
>  
> +/**
> + * igt_debugfs_simple_read:
> + * @filename: file name
> + * @buf: buffer where the contents will be stored, allocated by the
> caller
> + * @size: size of the buffer
> + *
> + * This function is similar to __igt_debugfs_read, the difference is
> that it
> + * expects the debugfs directory to be open and it's descriptor
> passed as the
> + * first argument.
> + *
> + * Returns:
> + * -errorno on failure or bytes read on success
> + */
> +int igt_debugfs_simple_read(int dir, const char *filename, char
> *buf, int size)
> +{
> +	int len;
> +
> +	len = igt_sysfs_read(dir, filename, buf, size - 1);
> +	if (len < 0)
> +		buf[0] = '\0';
> +	else
> +		buf[len] = '\0';
> +
> +	return len;
> +}
> +
>  /**
>   * __igt_debugfs_read:
>   * @filename: file name
>   * @buf: buffer where the contents will be stored, allocated by the
> caller
> - * @buf_size: size of the buffer
> + * @size: size of the buffer
>   *
>   * This function opens the debugfs file, reads it, stores the
> content in the
>   * provided buffer, then closes the file. Users should make sure
> that the buffer
>   * provided is big enough to fit the whole file, plus one byte.
>   */
> -void __igt_debugfs_read(int fd, const char *filename, char *buf, int
> buf_size)
> +void __igt_debugfs_read(int fd, const char *filename, char *buf, int
> size)
>  {
> -	int dir;
> -	int len;
> +	int dir = igt_debugfs_dir(fd);
>  
> -	dir = igt_debugfs_dir(fd);
> -	len = igt_sysfs_read(dir, filename, buf, buf_size - 1);
> -	if (len < 0)
> -		len = 0;
> -	buf[len] = '\0';
> +	igt_debugfs_simple_read(dir, filename, buf, size);
>  	close(dir);
>  }
>  
> diff --git a/lib/igt_debugfs.h b/lib/igt_debugfs.h
> index db634a82..ff8612dc 100644
> --- a/lib/igt_debugfs.h
> +++ b/lib/igt_debugfs.h
> @@ -37,7 +37,8 @@ char *igt_debugfs_path(int device, char *path, int
> pathlen);
>  int igt_debugfs_dir(int device);
>  
>  int igt_debugfs_open(int fd, const char *filename, int mode);
> -void __igt_debugfs_read(int fd, const char *filename, char *buf, int
> buf_size);
> +void __igt_debugfs_read(int fd, const char *filename, char *buf, int
> size);
> +int igt_debugfs_simple_read(int dir, const char *filename, char
> *buf, int size);
>  bool igt_debugfs_search(int fd, const char *filename, const char
> *substring);
>  
>  /**
> diff --git a/tests/kms_frontbuffer_tracking.c
> b/tests/kms_frontbuffer_tracking.c
> index 7ea2f697..822f3e74 100644
> --- a/tests/kms_frontbuffer_tracking.c
> +++ b/tests/kms_frontbuffer_tracking.c
> @@ -720,12 +720,9 @@ static void set_mode_for_params(struct
> modeset_params *params)
>  
>  static void __debugfs_read(const char *param, char *buf, int len)
>  {
> -	len = igt_sysfs_read(drm.debugfs, param, buf, len - 1);
> -	if (len < 0) {
> +	len = igt_debugfs_simple_read(drm.debugfs, param, buf, len);
> +	if (len < 0)
>  		igt_assert_eq(len, -ENODEV);
> -		len = 0;
> -	}
> -	buf[len] = '\0';
>  }
>  
>  static int __debugfs_write(const char *param, char *buf, int len)