drm/modes: Provide global mode_valid hook

Allow drivers to provide a device wide .mode_valid() hook in addition to
the already existing crtc/encoder/bridge/connector hooks. This can be
used to validate device/driver wide constraings without having to add
those to the other hooks. And since we call this hook also for user
modes later on in the modeset we don't have to worry about anything the
hook has already rejected.

I also have some further ideas for this hook. Eg. we could replace the
drm_mode_set_crtcinfo(HALVE_V) call in drm_mode_convert_umode()/etc.
with a driver specific variant via this hook. At least on i915 we would
like to pass CRTC_STEREO_DOUBLE to that function instead, and then
we could safely use the crtc_ timings in all our .mode_valid() hooks,
which would allow us to reuse those hooks for validating the
adjusted_mode during a modeset.

v2: Fix the language fails in the kernel docs (Daniel)

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171114183258.16976-10-ville.syrjala@linux.intel.com
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/drm_atomic.c

@@ -390,7 +390,7 @@ int drm_atomic_set_mode_prop_for_crtc(struct drm_crtc_state *state,
 
 	if (blob) {
 		if (blob->length != sizeof(struct drm_mode_modeinfo) ||
-		    drm_mode_convert_umode(&state->mode,
+		    drm_mode_convert_umode(state->crtc->dev, &state->mode,
 		                           (const struct drm_mode_modeinfo *)
 		                            blob->data))
 			return -EINVAL;

drivers/gpu/drm/drm_crtc.c

@@ -614,7 +614,7 @@ retry:
 			goto out;
 		}
 
-		ret = drm_mode_convert_umode(mode, &crtc_req->mode);
+		ret = drm_mode_convert_umode(dev, mode, &crtc_req->mode);
 		if (ret) {
 			DRM_DEBUG_KMS("Invalid mode\n");
 			goto out;

drivers/gpu/drm/drm_modes.c

@@ -1023,17 +1023,7 @@ bool drm_mode_equal_no_clocks_no_stereo(const struct drm_display_mode *mode1,
 }
 EXPORT_SYMBOL(drm_mode_equal_no_clocks_no_stereo);
 
-/**
- * drm_mode_validate_basic - make sure the mode is somewhat sane
- * @mode: mode to check
- *
- * Check that the mode timings are at least somewhat reasonable.
- * Any hardware specific limits are left up for each driver to check.
- *
- * Returns:
- * The mode status
- */
-enum drm_mode_status
+static enum drm_mode_status
 drm_mode_validate_basic(const struct drm_display_mode *mode)
 {
 	if (mode->type & ~DRM_MODE_TYPE_ALL)
@@ -1062,7 +1052,35 @@ drm_mode_validate_basic(const struct drm_display_mode *mode)
 
 	return MODE_OK;
 }
-EXPORT_SYMBOL(drm_mode_validate_basic);
+
+/**
+ * drm_mode_validate_driver - make sure the mode is somewhat sane
+ * @dev: drm device
+ * @mode: mode to check
+ *
+ * First do basic validation on the mode, and then allow the driver
+ * to check for device/driver specific limitations via the optional
+ * &drm_mode_config_helper_funcs.mode_valid hook.
+ *
+ * Returns:
+ * The mode status
+ */
+enum drm_mode_status
+drm_mode_validate_driver(struct drm_device *dev,
+			const struct drm_display_mode *mode)
+{
+	enum drm_mode_status status;
+
+	status = drm_mode_validate_basic(mode);
+	if (status != MODE_OK)
+		return status;
+
+	if (dev->mode_config.funcs->mode_valid)
+		return dev->mode_config.funcs->mode_valid(dev, mode);
+	else
+		return MODE_OK;
+}
+EXPORT_SYMBOL(drm_mode_validate_driver);
 
 /**
  * drm_mode_validate_size - make sure modes adhere to size constraints
@@ -1564,6 +1582,7 @@ void drm_mode_convert_to_umode(struct drm_mode_modeinfo *out,
 
 /**
  * drm_crtc_convert_umode - convert a modeinfo into a drm_display_mode
+ * @dev: drm device
  * @out: drm_display_mode to return to the user
  * @in: drm_mode_modeinfo to use
  *
@@ -1573,7 +1592,8 @@ void drm_mode_convert_to_umode(struct drm_mode_modeinfo *out,
  * Returns:
  * Zero on success, negative errno on failure.
  */
-int drm_mode_convert_umode(struct drm_display_mode *out,
+int drm_mode_convert_umode(struct drm_device *dev,
+			   struct drm_display_mode *out,
 			   const struct drm_mode_modeinfo *in)
 {
 	int ret = -EINVAL;
@@ -1600,7 +1620,7 @@ int drm_mode_convert_umode(struct drm_display_mode *out,
 	strncpy(out->name, in->name, DRM_DISPLAY_MODE_LEN);
 	out->name[DRM_DISPLAY_MODE_LEN-1] = 0;
 
-	out->status = drm_mode_validate_basic(out);
+	out->status = drm_mode_validate_driver(dev, out);
 	if (out->status != MODE_OK)
 		goto out;
 

drivers/gpu/drm/drm_probe_helper.c

@@ -499,7 +499,7 @@ retry:
 
 	list_for_each_entry(mode, &connector->modes, head) {
 		if (mode->status == MODE_OK)
-			mode->status = drm_mode_validate_basic(mode);
+			mode->status = drm_mode_validate_driver(dev, mode);
 
 		if (mode->status == MODE_OK)
 			mode->status = drm_mode_validate_size(mode, maxX, maxY);

include/drm/drm_mode_config.h

@@ -36,6 +36,7 @@ struct drm_device;
 struct drm_atomic_state;
 struct drm_mode_fb_cmd2;
 struct drm_format_info;
+struct drm_display_mode;
 
 /**
  * struct drm_mode_config_funcs - basic driver provided mode setting functions
@@ -101,6 +102,17 @@ struct drm_mode_config_funcs {
 	 */
 	void (*output_poll_changed)(struct drm_device *dev);
 
+	/**
+	 * @mode_valid:
+	 *
+	 * Device specific validation of display modes. Can be used to reject
+	 * modes that can never be supported. Only device wide constraints can
+	 * be checked here. crtc/encoder/bridge/connector specific constraints
+	 * should be checked in the .mode_valid() hook for each specific object.
+	 */
+	enum drm_mode_status (*mode_valid)(struct drm_device *dev,
+					   const struct drm_display_mode *mode);
+
 	/**
 	 * @atomic_check:
 	 *

include/drm/drm_modes.h

@@ -444,7 +444,8 @@ struct drm_display_mode *drm_mode_create(struct drm_device *dev);
 void drm_mode_destroy(struct drm_device *dev, struct drm_display_mode *mode);
 void drm_mode_convert_to_umode(struct drm_mode_modeinfo *out,
 			       const struct drm_display_mode *in);
-int drm_mode_convert_umode(struct drm_display_mode *out,
+int drm_mode_convert_umode(struct drm_device *dev,
+			   struct drm_display_mode *out,
 			   const struct drm_mode_modeinfo *in);
 void drm_mode_probed_add(struct drm_connector *connector, struct drm_display_mode *mode);
 void drm_mode_debug_printmodeline(const struct drm_display_mode *mode);
@@ -497,7 +498,8 @@ bool drm_mode_equal_no_clocks_no_stereo(const struct drm_display_mode *mode1,
 					const struct drm_display_mode *mode2);
 
 /* for use by the crtc helper probe functions */
-enum drm_mode_status drm_mode_validate_basic(const struct drm_display_mode *mode);
+enum drm_mode_status drm_mode_validate_driver(struct drm_device *dev,
+					      const struct drm_display_mode *mode);
 enum drm_mode_status drm_mode_validate_size(const struct drm_display_mode *mode,
 					    int maxX, int maxY);
 enum drm_mode_status