Re: [PATCH v11 09/11] drm: Expose modes with aspect ratio, only if requested

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

On Mon, Apr 23, 2018 at 11:19:08AM +0530, Nautiyal, Ankit K wrote:
> 
> 
> On 4/20/2018 7:52 PM, Ville Syrjälä wrote:
> > On Fri, Apr 20, 2018 at 07:01:49PM +0530, Nautiyal, Ankit K wrote:
> >> From: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
> >>
> >> We parse the EDID and add all the modes in the connector's modelist.
> >> This adds CEA modes with aspect ratio information too, regardless of
> >> whether user space requested this information or not.
> >>
> >> This patch prunes the modes with aspect-ratio information, from a
> >> connector's modelist, if the user-space has not set the aspect ratio
> >> DRM client cap. However if such a mode is unique in the list, it is
> >> kept in the list, with aspect-ratio flags reset.
> >>
> >> Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> >> Cc: Shashank Sharma <shashank.sharma@intel.com>
> >> Cc: Jose Abreu <jose.abreu@synopsys.com>
> >>
> >> Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
> >>
> >> V3: As suggested by Ville, modified the mechanism of pruning of modes
> >>      with aspect-ratio, if the aspect-ratio is not supported. Instead
> >>      of straight away pruning such a mode, the mode is retained with
> >>      aspect ratio bits set to zero, provided it is unique.
> >> V4: rebase
> >> V5: Addressed review comments from Ville:
> >>      -used a pointer to store last valid mode.
> >>      -avoided, modifying of picture_aspect_ratio in kernel mode,
> >>       instead only flags bits of user mode are reset (if aspect-ratio
> >>       is not supported).
> >> V6: As suggested by Ville, corrected the mode pruning logic and
> >>      elaborated the mode pruning logic and the assumptions taken.
> >> V7: rebase
> >> V8: rebase
> >> V9: rebase
> >> V10: rebase
> >> V11: Fixed the issue caused in kms_3d test, and enhanced the pruning
> >>       logic to correctly identify and prune modes with aspect-ratio,
> >>       if aspect-ratio cap is not set.
> >> ---
> >>   drivers/gpu/drm/drm_connector.c | 56 +++++++++++++++++++++++++++++++++++------
> >>   1 file changed, 48 insertions(+), 8 deletions(-)
> >>
> >> diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> >> index b3cde89..865ee354 100644
> >> --- a/drivers/gpu/drm/drm_connector.c
> >> +++ b/drivers/gpu/drm/drm_connector.c
> >> @@ -1531,15 +1531,35 @@ static struct drm_encoder *drm_connector_get_encoder(struct drm_connector *conne
> >>   	return connector->encoder;
> >>   }
> >>   
> >> -static bool drm_mode_expose_to_userspace(const struct drm_display_mode *mode,
> >> -					 const struct drm_file *file_priv)
> >> +static bool
> >> +drm_mode_expose_to_userspace(const struct drm_display_mode *mode,
> >> +			     const struct drm_display_mode *modelist,
> >> +			     const struct drm_file *file_priv)
> >>   {
> >>   	/*
> >>   	 * If user-space hasn't configured the driver to expose the stereo 3D
> >>   	 * modes, don't expose them.
> >>   	 */
> >> +	struct drm_display_mode *mode_itr;
> >> +
> >>   	if (!file_priv->stereo_allowed && drm_mode_is_stereo(mode))
> >>   		return false;
> >> +	/*
> >> +	 * If user-space hasn't configured the driver to expose the modes
> >> +	 * with aspect-ratio, don't expose them. However if such a mode
> >> +	 * is unique, let it be exposed, but reset the aspect-ratio flags
> >> +	 * while preparing the list of user-modes.
> >> +	 */
> >> +	if (!file_priv->aspect_ratio_allowed &&
> >> +	    mode->picture_aspect_ratio != HDMI_PICTURE_ASPECT_NONE) {
> >> +		list_for_each_entry(mode_itr, &modelist->head, head)
> >> +			if (drm_mode_match(mode_itr, mode,
> >> +					   DRM_MODE_MATCH_TIMINGS |
> >> +					   DRM_MODE_MATCH_CLOCK |
> >> +					   DRM_MODE_MATCH_FLAGS |
> >> +					   DRM_MODE_MATCH_3D_FLAGS))
> >> +				return false;
> >> +	}
> >>   
> >>   	return true;
> >>   }
> >> @@ -1550,7 +1570,7 @@ int drm_mode_getconnector(struct drm_device *dev, void *data,
> >>   	struct drm_mode_get_connector *out_resp = data;
> >>   	struct drm_connector *connector;
> >>   	struct drm_encoder *encoder;
> >> -	struct drm_display_mode *mode;
> >> +	struct drm_display_mode *mode, *tmp, modelist;
> >>   	int mode_count = 0;
> >>   	int encoders_count = 0;
> >>   	int ret = 0;
> >> @@ -1605,23 +1625,37 @@ int drm_mode_getconnector(struct drm_device *dev, void *data,
> >>   	out_resp->subpixel = connector->display_info.subpixel_order;
> >>   	out_resp->connection = connector->status;
> >>   
> >> +	INIT_LIST_HEAD(&modelist.head);
> > Why are we using a struct drm_display_mode to get a simple list_head?
> 
> Yes you are right, we can use the simple list_head here. I was trying to 
> use modelist as first mode, and goofed up.
> Its a mistake, I will correct it in next patchset.
> 
> >
> >> +
> >>   	/* delayed so we get modes regardless of pre-fill_modes state */
> >>   	list_for_each_entry(mode, &connector->modes, head)
> >> -		if (drm_mode_expose_to_userspace(mode, file_priv))
> >> +		if (drm_mode_expose_to_userspace(mode, &modelist,
> >> +						 file_priv)) {
> >> +			struct drm_display_mode *tmp_mode;
> >> +
> >> +			tmp_mode = drm_mode_duplicate(dev, mode);
> > Duplicating every mode seems rather wasteful. I suppose we could
> > just add another list_head to struct drm_display_mode for this
> > purpose. An alternative could be to somehow mark each exposed mode
> > and just walk the original connector mode list.
> 
> Agreed. Its indeed wasteful as we have to make the list in 2nd ioctl 
> call again.
> As you have suggested, to mark the exposed modes, can we add a flag in 
> drm_display_mode
> something like "to_be_exposed", which will be set in the first ioctl 
> call while determining the space.
> 2nd time, we can skip the marking process, and iterate over the 
> connector mode-list, making
> user-modes for only the modes that are marked?

No. You can't trust such a flag across two ioctl calls. It would have to
be protected by mode_config.mutex and as soon as you'd drop the lock
the flag would become invalid.

> 
> >> +			list_add_tail(&tmp_mode->head, &modelist.head);
> >>   			mode_count++;
> >> +		}
> >>   
> >>   	/*
> >>   	 * This ioctl is called twice, once to determine how much space is
> >>   	 * needed, and the 2nd time to fill it.
> >> +	 * The modes that need to be exposed to the user are maintained in the
> >> +	 * 'modelist'. When the ioctl is called first time to determine the,
> >> +	 * space, the modelist gets filled, to find the no. of modes. In the
> >> +	 * 2nd time, the user modes are filled, one by one from the modelist.
> >>   	 */
> >>   	if ((out_resp->count_modes >= mode_count) && mode_count) {
> >>   		copied = 0;
> >>   		mode_ptr = (struct drm_mode_modeinfo __user *)(unsigned long)out_resp->modes_ptr;
> >> -		list_for_each_entry(mode, &connector->modes, head) {
> >> -			if (!drm_mode_expose_to_userspace(mode, file_priv))
> >> -				continue;
> >> -
> >> +		list_for_each_entry(mode, &modelist.head, head) {
> >>   			drm_mode_convert_to_umode(&u_mode, mode);
> >> +			/*
> >> +			 * Reset aspect ratio flags of user-mode, if modes with
> >> +			 * aspect-ratio are not supported.
> >> +			 */
> >> +			drm_mode_filter_aspect_ratio_flags(file_priv, &u_mode);
> >>   			if (copy_to_user(mode_ptr + copied,
> >>   					 &u_mode, sizeof(u_mode))) {
> >>   				ret = -EFAULT;
> >> @@ -1651,6 +1685,12 @@ int drm_mode_getconnector(struct drm_device *dev, void *data,
> >>   	drm_modeset_unlock(&dev->mode_config.connection_mutex);
> >>   
> >>   out:
> >> +	list_for_each_entry_safe(mode, tmp, &modelist.head, head) {
> >> +		list_del(&mode->head);
> >> +		drm_mode_destroy(dev, mode);
> >> +	}
> >> +	list_del(&modelist.head);
> >> +
> >>   	drm_connector_put(connector);
> >>   
> >>   	return ret;
> >> -- 
> >> 2.7.4
> 

-- 
Ville Syrjälä
Intel
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