Den 27.07.2017 02.13, skrev Emil Velikov:
On 26 July 2017 at 19:41, Noralf Trønnes noralf@tronnes.org wrote:
Den 26.07.2017 14.05, skrev Emil Velikov:
Hi Noralf,
On 23 July 2017 at 20:16, Noralf Trønnes noralf@tronnes.org wrote:
Add a common drm_driver.dumb_map_offset function for GEM backed drivers.
Signed-off-by: Noralf Trønnes noralf@tronnes.org
drivers/gpu/drm/drm_gem.c | 35 +++++++++++++++++++++++++++++++++++ include/drm/drm_gem.h | 2 ++ 2 files changed, 37 insertions(+)
diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c index 5df028a..a8d396b 100644 --- a/drivers/gpu/drm/drm_gem.c +++ b/drivers/gpu/drm/drm_gem.c @@ -311,6 +311,41 @@ drm_gem_handle_delete(struct drm_file *filp, u32 handle) EXPORT_SYMBOL(drm_gem_handle_delete);
/**
- drm_gem_dumb_map_offset - return the fake mmap offset for a gem
object
- @file: drm file-private structure containing the gem object
- @dev: corresponding drm_device
- @handle: gem object handle
- @offset: return location for the fake mmap offset
- This implements the &drm_driver.dumb_map_offset kms driver callback
for
- drivers which use gem to manage their backing storage.
- Returns:
- 0 on success or a negative error code on failure.
- */
+int drm_gem_dumb_map_offset(struct drm_file *file, struct drm_device *dev,
u32 handle, u64 *offset)+{
struct drm_gem_object *obj;int ret;obj = drm_gem_object_lookup(file, handle);if (!obj)return -ENOENT;ret = drm_gem_create_mmap_offset(obj);With later patches one goes to reuse this helper instead of drm_gem_cma_dumb_map_offset(). At the same time, the latter does not have the drm_gem_create_mmap_offset() call we see here.
You're rigth, the cma library and a couple of other drivers if I recall correctly, call drm_gem_create_mmap_offset() during object creation. Daniel was of the opinion that this should happen when mmap is called. drm_gem_create_mmap_offset() is idempotent as the docs call it. Calling it a second time is ok, since it does nothing (needs to take a lock though).
I haven't removed drm_gem_create_mmap_offset() from the drivers that do it during object creation, trying to keep this from doing to much. The cma library will be changed though when I add the generic fb/gem helper.
I was not concerned about calling the function twice, but that it's not called at all ... Which doesn't seems to be the case - virtually all the .dumb_create callbacks effectively end up in __drm_gem_cma_create() which itself calls drm_gem_create_mmap_offset().
I should have looked deeper into the rabbit hole :-)
One thing that I forgot to mention: Depending on the tree you're working on, please grep through staging as well - the vbox drm driver got merged somewhat recently.
Meanwhile some drivers have their own offset function which is virtually identical to the original drm_gem_cma_dumb_map_offset. Yet those are left unchanged.
For example in cirrus [1]: There the only code difference seems to be an "upcast" followed immediately by a "downcast". Which should effectively be a noop.
The main reason for that is to try and keep this simple so I'm able to add my shmem/gem library in reasonable time :-) I didn't want to do changes that wasn't straight forward. But yes, the cirrus drivers looks quite straight forward and the functions isn't used by other parts of the driver. I looked at a driver (omap?) that had similar functions, and those where called from other parts of the driver, so I expected the same here I guess.
You say "some drivers", can you name them? Some drivers takes locks or do other stuff that made me skip them.
Agreed - keeping that cleanup separate might be the wise thing to do. Pardon if I came too impatient.
About a list - initial grep showed cirrus, bochs, qxl. Now, after having a more extensive look - cirrus, qxl, ast, nouveau, exynos, hibmc, mgag200, bochs, virtio.
All of those except exynos gets their offset from ttm_buffer_object->vma_node and not drm_gem_object.vma_node. Is it the same vma_node?
I'll add exynos in the second round, I missed that one.
Thanks for the scrutiny, it's appreciated.
Noralf.
On the "maybe" list - msm and omap have extra locking (is it still needed?) while armada has an import_attach restriction (where nobody else seems to bother?).
The remaining drivers seem a bit more complicated.
HTH Emil