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author | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-03-15 08:36:41 +0100 |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-03-15 08:36:41 +0100 |
commit | 83be46e944f630fde26ce03cb93f61a3066448e3 (patch) | |
tree | d94a48051f9311d99b615fa06adda2511f9cff2d /Documentation/gpu/todo.rst | |
parent | f8096ff38d5f62d8a2c473e1bec0163a1b2b86d8 (diff) | |
parent | 1e28eed17697bcf343c6743f0028cc3b5dd88bf0 (diff) | |
download | linux-83be46e944f630fde26ce03cb93f61a3066448e3.tar.gz linux-83be46e944f630fde26ce03cb93f61a3066448e3.tar.bz2 linux-83be46e944f630fde26ce03cb93f61a3066448e3.zip |
Merge v5.12-rc3 into char-misc-next
We need the char/misc fixes in here as well.
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'Documentation/gpu/todo.rst')
-rw-r--r-- | Documentation/gpu/todo.rst | 21 |
1 files changed, 21 insertions, 0 deletions
diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst index 40ccac61137e..22ce801e3a8d 100644 --- a/Documentation/gpu/todo.rst +++ b/Documentation/gpu/todo.rst @@ -613,6 +613,27 @@ Some of these date from the very introduction of KMS in 2008 ... 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 ============== |