ozone: Implement zero/one-copy texture for Ozone GBM.

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

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "ui/ozone/platform/drm/gpu/client_native_pixmap_vgem.h"
+
+#include <fcntl.h>
+#include <sys/mman.h>
+#include <xf86drm.h>
+
+#include "base/trace_event/trace_event.h"
+
+#if defined(OZONE_USE_VGEM_MAP)

[reveman, 2015/08/06 12:08:35]

why would you be building this file if VGEM is not enabled?

[dshwang, 2015/08/06 13:59:17]

Done. This file is compiled if only OZONE_USE_VGEM_MAP is defined. 

+#include <vgem_drm.h>
+#endif
+
+namespace ui {
+
+ClientNativePixmapVgem::ClientNativePixmapVgem(
+    const gfx::NativePixmapHandle& handle,
+    const base::FileDescriptor& vgem_handle,
+    const gfx::Size& size,
+    gfx::BufferFormat format)
+    : vgem_bo_handle_(0),
+      dma_buf_(handle.fd.fd),
+      vgem_fd_(vgem_handle),
+      size_(size),
+      format_(format),
+      stride_(handle.stride),
+      mmap_ptr_(nullptr) {
+  DCHECK(vgem_fd_.fd >= 0);

[reveman, 2015/08/06 12:08:35]

DCHECK_GT

[dshwang, 2015/08/06 13:59:17]

Done.

+  DCHECK(dma_buf_.get() >= 0);

[reveman, 2015/08/06 12:08:35]

DCHECK_GT

[dshwang, 2015/08/06 13:59:17]

Done.

+}
+
+bool ClientNativePixmapVgem::Initialize() {
+  DCHECK(vgem_fd_.fd);

[reveman, 2015/08/06 12:08:35]

why another dcheck here that is different from ctor?

[dshwang, 2015/08/06 13:59:17]

Done. removed Initialize()

+  int ret = drmPrimeFDToHandle(vgem_fd_.fd, dma_buf_.get(), &vgem_bo_handle_);
+  if (ret) {
+    PLOG(ERROR) << "drmPrimeFDToHandle failed, handle:" << vgem_bo_handle_;
+    return false;
+  }
+  return true;
+}
+
+ClientNativePixmapVgem::~ClientNativePixmapVgem() {
+  if (vgem_bo_handle_) {

[reveman, 2015/08/06 12:08:35]

note that this would be cleaner if you removed Initialize and didn't have to
deal with the possibility that it can fail. see my ImportFromHandle comment.

[dshwang, 2015/08/06 13:59:17]

Got it. Resolve it via Create(). Done.

+    struct drm_gem_close close;
+    memset(&close, 0, sizeof(close));

[reveman, 2015/08/06 12:08:35]

= { 0 } above instead?

[dshwang, 2015/08/06 13:59:17]

good idea. I copied the code from linux :)

+    close.handle = vgem_bo_handle_;
+    int ret = drmIoctl(vgem_fd_.fd, DRM_IOCTL_GEM_CLOSE, &close);
+    if (ret)
+      PLOG(ERROR) << "fail to free a vgem buffer. error:" << ret;
+    vgem_bo_handle_ = 0;
+  }
+}
+
+bool ClientNativePixmapVgem::Map(void** data) {
+#if defined(OZONE_USE_VGEM_MAP)
+  TRACE_EVENT0("gpu", "ClientNativePixmapVgem::Map");
+  DCHECK(!mmap_ptr_);
+  DCHECK(vgem_bo_handle_);
+
+  struct drm_mode_map_dumb mmap_arg;
+  memset(&mmap_arg, 0, sizeof(mmap_arg));
+  mmap_arg.handle = vgem_bo_handle_;
+
+  int ret = drmIoctl(vgem_fd_.fd, DRM_IOCTL_VGEM_MODE_MAP_DUMB, &mmap_arg);
+  if (ret) {
+    PLOG(ERROR) << "fail to map a vgem buffer. error:" << ret;
+    return false;
+  }
+  DCHECK(mmap_arg.offset);
+
+  size_t size = stride_ * size_.height();
+  mmap_ptr_ = mmap(nullptr, size, (PROT_READ | PROT_WRITE), MAP_SHARED,

[reveman, 2015/08/06 12:08:35]

can we keep it consistently mapped instead of doing that each time Map is
called?

[dshwang, 2015/08/06 13:59:17]

Good idea. It's possible at least in Intel Core architecture, because cpu cache
and gpu cache is coherent via last level cache snooping.
Keep it consistently mapped now. If we will find ARM or Intel ATOM has different
requirement, this code will be changed.

Currently vgem map is enabled in only Intel Core architecture;
https://chromium-review.googlesource.com/#/c/288890/

+                   vgem_fd_.fd, mmap_arg.offset);
+  DCHECK(mmap_ptr_ != MAP_FAILED);
+  *data = mmap_ptr_;
+  return true;
+#else
+  NOTREACHED();
+  return false;
+#endif
+}
+
+void ClientNativePixmapVgem::Unmap() {
+#if defined(OZONE_USE_VGEM_MAP)
+  TRACE_EVENT0("gpu", "ClientNativePixmapVgem::Unmap");
+  DCHECK(mmap_ptr_);
+  DCHECK(vgem_bo_handle_);
+
+  size_t size = stride_ * size_.height();
+  int ret = munmap(mmap_ptr_, size);
+  DCHECK(!ret);
+  mmap_ptr_ = nullptr;
+#else
+  NOTREACHED();
+#endif
+}
+void ClientNativePixmapVgem::GetStride(int* stride) const {
+  *stride = stride_;
+}
+
+}  // namespace ui