Hi Ben, Please refer to comments below.
On 02/22/2012 08:29 PM, Ben Widawsky wrote:
dma-buf export implementation. Heavily influenced by Dave Airlie's proof of concept work.
Cc: Daniel Vetterdaniel.vetter@ffwll.ch Cc: Dave Airlieairlied@redhat.com Signed-off-by: Ben Widawskyben@bwidawsk.net
drivers/gpu/drm/vgem/Makefile | 2 +- drivers/gpu/drm/vgem/vgem_dma_buf.c | 128 +++++++++++++++++++++++++++++++++++ drivers/gpu/drm/vgem/vgem_drv.c | 6 ++ drivers/gpu/drm/vgem/vgem_drv.h | 7 ++ 4 files changed, 142 insertions(+), 1 deletions(-) create mode 100644 drivers/gpu/drm/vgem/vgem_dma_buf.c
[snip]
+int vgem_prime_to_fd(struct drm_device *dev, struct drm_file *file,
uint32_t handle, int *prime_fd)+{
- struct drm_vgem_file_private *file_priv = file->driver_priv;
- struct drm_vgem_gem_object *obj;
- int ret;
- DRM_DEBUG_PRIME("Request fd for handle %d\n", handle);
- obj = to_vgem_bo(drm_gem_object_lookup(dev, file, handle));
- if (!obj)
return -EBADF;- /* This means a user has already called get_fd on this */
- if (obj->base.prime_fd != -1) {
DRM_DEBUG_PRIME("User requested a previously exported buffer ""%d %d\n", handle, obj->base.prime_fd);drm_gem_object_unreference(&obj->base);goto out_fd;
IMO, it is not safe to cache a number of file descriptor. This number may unexpectedly become invalid introducing a bug. Please refer to the scenario: - application possess a GEM buffer called A - call DRM_IOCTL_PRIME_HANDLE_TO_FD on A to obtain a file descriptor fd_A - application calls fd_B = dup(fd_A). Now both fd_A and fd_B point to the same DMABUF instance. - application calls close(fd_A), now fd_A is no longer a valid file descriptor - application tries to export the buffer again and calls ioctl DRM_IOCTL_PRIME_HANDLE_TO_FD on GEM buffer. The field obj->base.prime_fd is already set to fd_A so value fd_A is returned to userspace. Notice that this is a bug because fd_A is no longer valid.
I think that field prime_fd should be removed because it is too unreliable. The driver should call dma_buf_fd every time when the buffer is exported.
- }
- /* Make a dma buf out of our vgem object */
- obj->base.export_dma_buf = dma_buf_export(obj,&vgem_dmabuf_ops,
obj->base.size,VGEM_FD_PERMS);- if (IS_ERR(obj->base.export_dma_buf)) {
DRM_DEBUG_PRIME("export fail\n");return PTR_ERR(obj->base.export_dma_buf);- } else
obj->base.prime_fd = dma_buf_fd(obj->base.export_dma_buf);- mutex_lock(&dev->prime_mutex);
- ret = drm_prime_insert_fd_handle_mapping(&file_priv->prime,
obj->base.export_dma_buf,handle);- WARN_ON(ret);
- ret = drm_prime_add_dma_buf(dev,&obj->base);
- mutex_unlock(&dev->prime_mutex);
- if (ret)
return ret;+out_fd:
- *prime_fd = obj->base.prime_fd;
- return 0;
+}
Regards, Tomasz Stanislawski