Re: [Linaro-mm-sig] [PATCH 6/7] drm/vgem: import support

On Wed, 22 Feb 2012 20:29:19 +0100, Ben Widawsky ben@bwidawsk.net wrote:

dma-buf import support. The function definitely needs some cleanup.

When reading through this code, there are 3 cases to consider:

1. vgem exporter, vgem importer, same fd
2. vgem exporter, vgem importer, different fd
3. X expoter, vgem importer - not yet tested

See the comments in the code for detailed explanation.

Cc: Daniel Vetter daniel.vetter@ffwll.ch Cc: Dave Airlie airlied@redhat.com Signed-off-by: Ben Widawsky ben@bwidawsk.net

---

drivers/gpu/drm/vgem/vgem_dma_buf.c | 120 +++++++++++++++++++++++++++++++++++ 1 files changed, 120 insertions(+), 0 deletions(-)

diff --git a/drivers/gpu/drm/vgem/vgem_dma_buf.c b/drivers/gpu/drm/vgem/vgem_dma_buf.c index eca9445..92c1823 100644 --- a/drivers/gpu/drm/vgem/vgem_dma_buf.c +++ b/drivers/gpu/drm/vgem/vgem_dma_buf.c @@ -120,9 +120,129 @@ out_fd: return 0; } +/*

• • Convert a dma-buf fd to a drm object handle, creating new object/handle as
• • needed.
• • There are 2 "interesting" cases we have to consider. The other, less interesting
• • case is when importer == exporter, and drm_files are the same.
• • vgem exporter
• • The original exporter may or may not still hold a reference to the
• • object by the time we reach here. Once we get a dma_buf reference though
• • we know the original object cannot go away. Next we grab the prime mutex
• • to prevent our lists from being screwed up from under us. We should next
• • find the object in our global dma_buf hash. To make everything cool
• • though we need to

• • create a handle for the importer
    

• • add the handle to the per file list
    

• • drop the dma_buf reference
    

• •   the object can't go away due to us owning a file handle for it.
    

• • In the end there should be 2 handle references, and 1 dma-buf reference.
• • other exporter
• • This case is very similar to the previous one. The primary difference is we
• • do not want to drop the dma_buf reference since we know nothing about the
• • reference counting from the exporter. So instead, we hold the dma_buf
• • reference, but can drop the object reference. In the end of this case there
• • should be 1 handle reference, and 1 dma-buf reference.
• */

int vgem_prime_to_handle(struct drm_device *dev, struct drm_file *file, int prime_fd, uint32_t *handle) {

• struct drm_vgem_file_private *file_priv = file->driver_priv;
• struct drm_vgem_gem_object *vobj = NULL;
• struct drm_gem_object *obj = NULL;
• struct dma_buf *dma_buf;
• struct dma_buf_attachment *attach = NULL;
• struct sg_table *sg = NULL;
• bool drop_dma_buf_ref = false;
• int ret;
• dma_buf = dma_buf_get(prime_fd);
• if (IS_ERR(dma_buf))

• return PTR_ERR(dma_buf);
  

• mutex_lock(&dev->prime_mutex);
• /* First check that we don't dup on this file */
• ret = drm_prime_lookup_fd_handle_mapping(&file_priv->prime, dma_buf,

• 				 handle);
  

• if (ret == 0) {

• DRM_DEBUG_PRIME("file_priv has an object for this dma_buf\n");
  

• dma_buf_put(dma_buf);
  

• mutex_unlock(&dev->prime_mutex);
  

• return 0;
  

• }
• /* Now check if we've already created/imported this object */
• ret = drm_prime_lookup_obj(dev, dma_buf, &obj);
• if (ret == 0 && obj != NULL) {

• DRM_DEBUG_PRIME("driver has an object for this dma_buf\n");
  

• drop_dma_buf_ref = true;
  

• vobj = to_vgem_bo(obj);
  

• goto handle_create;
  

• }
• DRM_DEBUG_PRIME("Creating a new object for dma_buf\n");
• attach = dma_buf_attach(dma_buf, dev->dev);
• if (IS_ERR(attach)) {

• ret = PTR_ERR(attach);
  

• goto fail_put;
  

• }
• sg = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
• if (IS_ERR(sg)) {

• ret = PTR_ERR(sg);
  

• goto fail_detach;
  

• }
• vobj = kzalloc(sizeof(*vobj), GFP_KERNEL);
• if (vobj == NULL) {

• ret = -ENOMEM;
  

• goto fail_unmap;
  

• }
• /* As a result of this mmap will not work -yet- */
• ret = drm_gem_private_object_init(dev, &vobj->base, dma_buf->size);
• if (ret) {

• kfree(vobj);
  

• ret = -ENOMEM;
  

• goto fail_unmap;
  

• }
• obj = &vobj->base;

Don't we need to store the backing attachment and prime_fd on the newly created vgem obj?

+handle_create:

• ret = drm_gem_handle_create(file, obj, handle);
• if (ret)

• return ret;
  

• ret = drm_prime_insert_fd_handle_mapping(&file_priv->prime,

• 				 dma_buf, *handle);
  

• if (ret)

• goto fail_handle;
  

• mutex_unlock(&dev->prime_mutex);
• if (drop_dma_buf_ref) {

• /* This should mean we found this in the global hash */
  

• dma_buf_put(dma_buf);
  

• } else {

• /* Handle holds the reference for the object we created */
  

• drm_gem_object_unreference(obj);
  

• }
• return 0;

+fail_handle:

• drm_gem_object_handle_unreference_unlocked(obj);

+fail_unmap:

• dma_buf_unmap_attachment(attach, sg);

+fail_detach:

• dma_buf_detach(dma_buf, attach);

+fail_put:

• dma_buf_put(dma_buf);
• mutex_unlock(&dev->prime_mutex);
• return 0;

}