Re: [PATCH] drm/crc: Only report a single overflow when a CRC fd is opened

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Wed, Apr 18, 2018 at 02:51:21PM +0200, Maarten Lankhorst wrote:
> This reduces the amount of spam when you debug a CRC reading
> program.
> 
> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> ---
>  drivers/gpu/drm/drm_debugfs_crc.c | 9 ++++++++-
>  include/drm/drm_debugfs_crc.h     | 3 ++-
>  2 files changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_debugfs_crc.c b/drivers/gpu/drm/drm_debugfs_crc.c
> index 9f8312137cad..5a052c511e62 100644
> --- a/drivers/gpu/drm/drm_debugfs_crc.c
> +++ b/drivers/gpu/drm/drm_debugfs_crc.c
> @@ -139,6 +139,7 @@ static int crtc_crc_data_count(struct drm_crtc_crc *crc)
>  static void crtc_crc_cleanup(struct drm_crtc_crc *crc)
>  {
>  	kfree(crc->entries);
> +	crc->overflow = false;
>  	crc->entries = NULL;
>  	crc->head = 0;
>  	crc->tail = 0;
> @@ -391,8 +392,14 @@ int drm_crtc_add_crc_entry(struct drm_crtc *crtc, bool has_frame,
>  	tail = crc->tail;
>  
>  	if (CIRC_SPACE(head, tail, DRM_CRC_ENTRIES_NR) < 1) {
> +		bool overflow = crc->overflow;

'was_overflow' or something to indicate this is the old value?

> +
> +		crc->overflow = true;
>  		spin_unlock(&crc->lock);
> -		DRM_ERROR("Overflow of CRC buffer, userspace reads too slow.\n");
> +
> +		if (!overflow)
> +			DRM_ERROR("Overflow of CRC buffer, userspace reads too slow.\n");

would make this a bit less confusing perhaps. Now it reads as
"if (no overflow) DRM_ERROR("we have an overflow");" which makes no
sense on the first glance.

Apart from that
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

> +
>  		return -ENOBUFS;
>  	}
>  
> diff --git a/include/drm/drm_debugfs_crc.h b/include/drm/drm_debugfs_crc.h
> index 7d63b1d4adb9..b225eeb30d05 100644
> --- a/include/drm/drm_debugfs_crc.h
> +++ b/include/drm/drm_debugfs_crc.h
> @@ -43,6 +43,7 @@ struct drm_crtc_crc_entry {
>   * @lock: protects the fields in this struct
>   * @source: name of the currently configured source of CRCs
>   * @opened: whether userspace has opened the data file for reading
> + * @overflow: whether an overflow occured.
>   * @entries: array of entries, with size of %DRM_CRC_ENTRIES_NR
>   * @head: head of circular queue
>   * @tail: tail of circular queue
> @@ -52,7 +53,7 @@ struct drm_crtc_crc_entry {
>  struct drm_crtc_crc {
>  	spinlock_t lock;
>  	const char *source;
> -	bool opened;
> +	bool opened, overflow;
>  	struct drm_crtc_crc_entry *entries;
>  	int head, tail;
>  	size_t values_cnt;
> -- 
> 2.17.0
> 
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-- 
Ville Syrjälä
Intel
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