[PATCH 1/7] drm: Don't overwrite UNVERFIED mode status to OK

[Daniel Vetter]

On Thu, Dec 03, 2015 at 11:14:09PM +0200, ville.syrjala at linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> The way the mode probing works is this:
> 1. All modes currently on the mode list are marked as UNVERIFIED
> 2. New modes are on the probed_modes list (they start with
>    status OK)
> 3. Modes are moved from the probed_modes list to the actual
>    mode list. If a mode already on the mode list is deemed
>    to match one of the probed modes, the duplicate is dropped
>    and the mode status updated to OK. After this the
>    probed_modes list will be empty.
> 4. All modes on the mode list are verified to not violate any
>    constraints. Any that do are marked as such.
> 5. Any mode left with a non-OK status is pruned from the list,
>    with an appropriate debug message.

This would look really pretty as a kerneldoc addition to
probe_single_connector(). And with asciidoc we can even do pretty ordered
lists like these. Can you please follow-up with a patch for that?

> 
> What all this means is that any mode on the original list that
> didn't have a duplicate on the probed_modes list, should be left
> with status UNVERFIED (or previously could have been left with
> some other status, but never OK).
> 
> I broke that in
> commit 05acaec334fc ("drm: Reorganize probed mode validation")
> by always assigning something to the mode->status during the validation
> step. So any mode from the old list that still passed the validation
> would be left on the list with status OK in the end.
> 
> Fix this by not doing the basic mode validation unless the mode
> already has status OK (meaning it came from the probed_modes list,
> or at least a duplicate of it was on that list). This way we will
> correctly prune away any mode from the old mode list that didn't
> appear on the probed_modes list.
> 
> Cc: stable at vger.kernel.org
> Cc: Adam Jackson <ajax at redhat.com>
> Fixes: 05acaec334fc ("drm: Reorganize probed mode validation")
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>

Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>

> ---
>  drivers/gpu/drm/drm_probe_helper.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c
> index 94ba39e34299..b9b3bd9349ff 100644
> --- a/drivers/gpu/drm/drm_probe_helper.c
> +++ b/drivers/gpu/drm/drm_probe_helper.c
> @@ -229,7 +229,8 @@ static int drm_helper_probe_single_connector_modes_merge_bits(struct drm_connect
>  		mode_flags |= DRM_MODE_FLAG_3D_MASK;
>  
>  	list_for_each_entry(mode, &connector->modes, head) {
> -		mode->status = drm_mode_validate_basic(mode);
> +		if (mode->status == MODE_OK)
> +			mode->status = drm_mode_validate_basic(mode);
>  
>  		if (mode->status == MODE_OK)
>  			mode->status = drm_mode_validate_size(mode, maxX, maxY);
> -- 
> 2.4.10
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch