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Diffstat (limited to 'Documentation/gpu/todo.rst')
| -rw-r--r-- | Documentation/gpu/todo.rst | 23 |
1 files changed, 22 insertions, 1 deletions
diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst index 0631b9b323d5..1b4b64b71c7e 100644 --- a/Documentation/gpu/todo.rst +++ b/Documentation/gpu/todo.rst @@ -571,6 +571,27 @@ Contact: Daniel Vetter Level: Intermediate +Remove automatic page mapping from dma-buf importing +---------------------------------------------------- + +When importing dma-bufs, the dma-buf and PRIME frameworks automatically map +imported pages into the importer's DMA area. drm_gem_prime_fd_to_handle() and +drm_gem_prime_handle_to_fd() require that importers call dma_buf_attach() +even if they never do actual device DMA, but only CPU access through +dma_buf_vmap(). This is a problem for USB devices, which do not support DMA +operations. + +To fix the issue, automatic page mappings should be removed from the +buffer-sharing code. Fixing this is a bit more involved, since the import/export +cache is also tied to &drm_gem_object.import_attach. Meanwhile we paper over +this problem for USB devices by fishing out the USB host controller device, as +long as that supports DMA. Otherwise importing can still needlessly fail. + +Contact: Thomas Zimmermann <tzimmermann@suse.de>, Daniel Vetter + +Level: Advanced + + Better Testing ============== @@ -644,7 +665,7 @@ for fbdev. https://patchwork.freedesktop.org/patch/306579/ - [RFC PATCH v2 00/13] Kernel based bootsplash - https://lkml.org/lkml/2017/12/13/764 + https://lore.kernel.org/r/20171213194755.3409-1-mstaudt@suse.de Contact: Sam Ravnborg |