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| author | David S. Miller <davem@davemloft.net> | 2021-03-26 01:31:22 +0300 |
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| committer | David S. Miller <davem@davemloft.net> | 2021-03-26 01:31:22 +0300 |
| commit | efd13b71a3fa31413f8d15342e01d44b60b0a432 (patch) | |
| tree | 2ed1b299e25538c5a60485a1047507b49d3e0ecf /Documentation/gpu/todo.rst | |
| parent | 84c7f6c33f42a12eb036ebf0f0e3670799304120 (diff) | |
| parent | 002322402dafd846c424ffa9240a937f49b48c42 (diff) | |
| download | linux-efd13b71a3fa31413f8d15342e01d44b60b0a432.tar.xz | |
Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net
Signed-off-by: David S. Miller <davem@davemloft.net>
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 ============== |