ozone: Allocate scanout buffer according to KMS modifiers

ui/ozone/platform/drm/gpu/hardware_display_plane.cc

Index: ui/ozone/platform/drm/gpu/hardware_display_plane.cc
diff --git a/ui/ozone/platform/drm/gpu/hardware_display_plane.cc b/ui/ozone/platform/drm/gpu/hardware_display_plane.cc
index 54f59188aba79c9e711776d76a89bfae75056987..a329edc8db79099a4c5f2e7014a5687a971a71ec 100644
--- a/ui/ozone/platform/drm/gpu/hardware_display_plane.cc
+++ b/ui/ozone/platform/drm/gpu/hardware_display_plane.cc
@@ -5,6 +5,7 @@
 #include "ui/ozone/platform/drm/gpu/hardware_display_plane.h"
 
 #include <drm_fourcc.h>
+#include <drm_mode.h>
 
 #include "base/logging.h"
 #include "ui/ozone/platform/drm/gpu/drm_device.h"
@@ -54,11 +55,14 @@ bool HardwareDisplayPlane::CanUseForCrtc(uint32_t crtc_index) {
   return possible_crtcs_ & (1 << crtc_index);
 }
 
-bool HardwareDisplayPlane::Initialize(DrmDevice* drm,
-                                      const std::vector<uint32_t>& formats,
-                                      bool is_dummy,
-                                      bool test_only) {
+bool HardwareDisplayPlane::Initialize(
+    DrmDevice* drm,
+    const std::vector<uint32_t>& formats,
+    const std::vector<struct drm_format_modifier>& format_modifiers,
+    bool is_dummy,
+    bool test_only) {
   supported_formats_ = formats;
+  supported_format_modifiers_ = format_modifiers;
 
   if (test_only)
     return true;
@@ -112,6 +116,26 @@ const std::vector<uint32_t>& HardwareDisplayPlane::supported_formats() const {
   return supported_formats_;
 }
 
+std::vector<uint64_t> HardwareDisplayPlane::ModifiersForFormat(
+    uint32_t format) {
+  uint32_t format_index = 0;
+  std::vector<uint64_t> modifiers;
+
+  for (const auto& f : supported_formats_) {

[Daniele Castagna, 2016/12/20 18:03:28]

This is a vector of ints. In general, it doesn't make much sense to get a
reference to a int.

While you're there, you could probably just replace this with:

uint32_t format_index = std::find(supported_format_.begin(),
supported_format_.end(), format) - supported_format.begin();
The DCHECK would still apply.

Btw, what happens when this is a dummy plane?

[hoegsberg1, 2016/12/22 23:05:21]

Sure. I guess that's idiomatic, but it's a lot harder to read.
We initialize with an empty vector for modifiers. This function returns an empty
vector and buffer allocation falls back to old-fashion use-flag entry point.

+    if (f == format)
+      break;
+    format_index++;
+  }
+  DCHECK_LT(format_index, supported_formats_.size());
+
+  for (const auto& modifier : supported_format_modifiers_) {

[Daniele Castagna, 2016/12/20 18:03:28]

No need to use a ref for built in types.

[hoegsberg1, 2016/12/22 23:05:21]

We're iterating through std:vector<struct drm_format_modifier> here.

+    if (modifier.formats & (1 << format_index))
+      modifiers.push_back(modifier.modifier);
+  }
+
+  return modifiers;
+}
+
 bool HardwareDisplayPlane::InitializeProperties(
     DrmDevice* drm,
     const ScopedDrmObjectPropertyPtr& plane_props) {