Pull the parameter checking from drm_primary_helper_update() out into
its own function; drivers that provide their own setplane()
implementations rather than using the helper may still want to share
this parameter checking logic.

A few of the checks here were also updated based on suggestions by
Ville Syrj?l?.

v2:
  - Pass src/dest/clip rects and min/max scaling down to helper to avoid
    duplication of effort between helper and drivers (suggested by
    Ville).
  - Allow caller to specify whether the primary plane should be
    updatable while the crtc is disabled.

Cc: Ville Syrj?l? <ville.syrjala at linux.intel.com>
Cc: dri-devel at lists.freedesktop.org
Signed-off-by: Matt Roper <matthew.d.roper at intel.com>
---
 drivers/gpu/drm/drm_plane_helper.c | 123 ++++++++++++++++++++++++++++---------
 include/drm/drm_plane_helper.h     |  24 +++++++-
 2 files changed, 116 insertions(+), 31 deletions(-)

diff --git a/drivers/gpu/drm/drm_plane_helper.c 
b/drivers/gpu/drm/drm_plane_helper.c
index b601233..11e8b82 100644
--- a/drivers/gpu/drm/drm_plane_helper.c
+++ b/drivers/gpu/drm/drm_plane_helper.c
@@ -26,6 +26,7 @@
 #include <linux/list.h>
 #include <drm/drmP.h>
 #include <drm/drm_rect.h>
+#include <drm/drm_plane_helper.h>

 #define SUBPIXEL_MASK 0xffff

@@ -66,6 +67,77 @@ static int get_connectors_for_crtc(struct drm_crtc *crtc,
 }

 /**
+ * drm_primary_helper_check_update() - Check primary plane update for validity
+ * @plane: plane object to update
+ * @crtc: owning CRTC of owning plane
+ * @fb: framebuffer to flip onto plane
+ * @src: source coordinates in 16.16 fixed point
+ * @dest: integer destination coordinates
+ * @clip: integer clipping coordinates
+ * @min_scale: minimum @src:@dest scaling factor in 16.16 fixed point
+ * @max_scale: maximum @src:@dest scaling factor in 16.16 fixed point
+ * @can_position: is it legal to position the primary plane such that it
+ *                doesn't cover the entire crtc?
+ * @can_update_disabled: can the primary plane be updated while the crtc
+ *                       is disabled?
+ * @visible: output parameter indicating whether plane is still visible after
+ *           clipping
+ *
+ * Checks that a desired primary plane update is valid.  Drivers that provide
+ * their own primary plane handling may still wish to call this function to
+ * avoid duplication of error checking code.
+ *
+ * RETURNS:
+ * Zero if update appears valid, error code on failure
+ */
+int drm_primary_helper_check_update(struct drm_plane *plane,
+                                   struct drm_crtc *crtc,
+                                   struct drm_framebuffer *fb,
+                                   struct drm_rect *src,
+                                   struct drm_rect *dest,
+                                   const struct drm_rect *clip,
+                                   int min_scale,
+                                   int max_scale,
+                                   bool can_position,
+                                   bool can_update_disabled,
+                                   bool *visible)
+{
+       int hscale, vscale;
+
+       if (!crtc->enabled && !can_update_disabled) {
+               DRM_DEBUG_KMS("Cannot update primary plane of a disabled 
CRTC.\n");
+               return -EINVAL;
+       }
+
+       /* Check scaling */
+       hscale = drm_rect_calc_hscale(src, dest, min_scale, max_scale);
+       vscale = drm_rect_calc_vscale(src, dest, min_scale, max_scale);
+       if (hscale < 0 || vscale < 0) {
+               DRM_DEBUG_KMS("Invalid scaling of primary plane\n");
+               return -ERANGE;
+       }
+
+       *visible = drm_rect_clip_scaled(src, dest, clip, hscale, vscale);
+       if (!visible)
+               /*
+                * Primary plane isn't visible; some drivers can handle this
+                * so we just return success here.  Drivers that can't
+                * (including those that use the primary plane helper's
+                * update function) will return an error from their
+                * update_plane handler.
+                */
+               return 0;
+
+       if (!can_position && !drm_rect_equals(dest, clip)) {
+               DRM_DEBUG_KMS("Primary plane must cover entire CRTC\n");
+               return -EINVAL;
+       }
+
+       return 0;
+}
+EXPORT_SYMBOL(drm_primary_helper_check_update);
+
+/**
  * drm_primary_helper_update() - Helper for primary plane update
  * @plane: plane object to update
  * @crtc: owning CRTC of owning plane
@@ -113,51 +185,42 @@ int drm_primary_helper_update(struct drm_plane *plane, 
struct drm_crtc *crtc,
                .x = src_x >> 16,
                .y = src_y >> 16,
        };
+       struct drm_rect src = {
+               .x1 = src_x,
+               .y1 = src_y,
+               .x2 = src_x + src_w,
+               .y2 = src_y + src_h,
+       };
        struct drm_rect dest = {
                .x1 = crtc_x,
                .y1 = crtc_y,
                .x2 = crtc_x + crtc_w,
                .y2 = crtc_y + crtc_h,
        };
-       struct drm_rect clip = {
+       const struct drm_rect clip = {
                .x2 = crtc->mode.hdisplay,
                .y2 = crtc->mode.vdisplay,
        };
        struct drm_connector **connector_list;
        int num_connectors, ret;
+       bool visible;

-       if (!crtc->enabled) {
-               DRM_DEBUG_KMS("Cannot update primary plane of a disabled 
CRTC.\n");
-               return -EINVAL;
-       }
-
-       /* Disallow subpixel positioning */
-       if ((src_x | src_y | src_w | src_h) & SUBPIXEL_MASK) {
-               DRM_DEBUG_KMS("Primary plane does not support subpixel 
positioning\n");
-               return -EINVAL;
-       }
-
-       /* Disallow scaling */
-       src_w >>= 16;
-       src_h >>= 16;
-       if (crtc_w != src_w || crtc_h != src_h) {
-               DRM_DEBUG_KMS("Can't scale primary plane\n");
-               return -EINVAL;
-       }
-
-       /* Make sure primary plane covers entire CRTC */
-       drm_rect_intersect(&dest, &clip);
-       if (dest.x1 != 0 || dest.y1 != 0 ||
-           dest.x2 != crtc->mode.hdisplay || dest.y2 != crtc->mode.vdisplay) {
-               DRM_DEBUG_KMS("Primary plane must cover entire CRTC\n");
-               return -EINVAL;
-       }
-
-       /* Framebuffer must be big enough to cover entire plane */
-       ret = drm_crtc_check_viewport(crtc, crtc_x, crtc_y, &crtc->mode, fb);
+       ret = drm_primary_helper_check_update(plane, crtc, fb,
+                                             &src, &dest, &clip,
+                                             DRM_PLANE_HELPER_NO_SCALING,
+                                             DRM_PLANE_HELPER_NO_SCALING,
+                                             false, false, &visible);
        if (ret)
                return ret;

+       if (!visible)
+               /*
+                * Primary plane isn't visible.  Note that unless a driver
+                * provides their own disable function, this will just
+                * wind up returning -EINVAL to userspace.
+                */
+               return plane->funcs->disable_plane(plane);
+
        /* Find current connectors for CRTC */
        num_connectors = get_connectors_for_crtc(crtc, NULL, 0);
        BUG_ON(num_connectors == 0);
diff --git a/include/drm/drm_plane_helper.h b/include/drm/drm_plane_helper.h
index 09824be..05e1357 100644
--- a/include/drm/drm_plane_helper.h
+++ b/include/drm/drm_plane_helper.h
@@ -24,6 +24,17 @@
 #ifndef DRM_PLANE_HELPER_H
 #define DRM_PLANE_HELPER_H

+#include <drm/drm_rect.h>
+
+/*
+ * Drivers that don't allow primary plane scaling may pass this macro in place
+ * of the min/max scale parameters of the update checker function.
+ *
+ * Due to src being in 16.16 fixed point and dest being in integer pixels,
+ * 1<<16 represents no scaling.
+ */
+#define DRM_PLANE_HELPER_NO_SCALING (1<<16)
+
 /**
  * DOC: plane helpers
  *
@@ -31,6 +42,17 @@
  * planes.
  */

+extern int drm_primary_helper_check_update(struct drm_plane *plane,
+                                          struct drm_crtc *crtc,
+                                          struct drm_framebuffer *fb,
+                                          struct drm_rect *src,
+                                          struct drm_rect *dest,
+                                          const struct drm_rect *clip,
+                                          int min_scale,
+                                          int max_scale,
+                                          bool can_position,
+                                          bool can_update_disabled,
+                                          bool *visible);
 extern int drm_primary_helper_update(struct drm_plane *plane,
                                     struct drm_crtc *crtc,
                                     struct drm_framebuffer *fb,
@@ -42,7 +64,7 @@ extern int drm_primary_helper_disable(struct drm_plane 
*plane);
 extern void drm_primary_helper_destroy(struct drm_plane *plane);
 extern const struct drm_plane_funcs drm_primary_helper_funcs;
 extern struct drm_plane *drm_primary_helper_create_plane(struct drm_device 
*dev,
-                                                        uint32_t *formats,
+                                                        const uint32_t 
*formats,
                                                         int num_formats);


-- 
1.8.5.1

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