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| author | Michal Miroslaw <mirq-linux@rere.qmqm.pl> | 2011-07-26 16:08:51 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2011-07-26 16:49:45 -0700 |
| commit | 3f0fb4e85b3842a2606c647c0a66afe2073574b4 (patch) | |
| tree | 071ed60729b9c14bc88db707d0e4020cf717184c /Documentation/DMA-API-HOWTO.txt | |
| parent | 91f6cdf86e8a2bd9b9c292a750179dc2c728a2d4 (diff) | |
| download | linux-3f0fb4e85b3842a2606c647c0a66afe2073574b4.tar.gz linux-3f0fb4e85b3842a2606c647c0a66afe2073574b4.tar.bz2 linux-3f0fb4e85b3842a2606c647c0a66afe2073574b4.zip | |
Documentation/DMA-API-HOWTO.txt: fix misleading example
See: DMA-API.txt, part Id, DMA_FROM_DEVICE description.
Signed-off-by: Michal Miroslaw <mirq-linux@rere.qmqm.pl>
Cc: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation/DMA-API-HOWTO.txt')
| -rw-r--r-- | Documentation/DMA-API-HOWTO.txt | 12 |
1 files changed, 6 insertions, 6 deletions
diff --git a/Documentation/DMA-API-HOWTO.txt b/Documentation/DMA-API-HOWTO.txt index d568bc235bc0..a0b6250add79 100644 --- a/Documentation/DMA-API-HOWTO.txt +++ b/Documentation/DMA-API-HOWTO.txt @@ -613,13 +613,13 @@ to use the dma_sync_*() interfaces. pass_to_upper_layers(cp->rx_buf); make_and_setup_new_rx_buf(cp); } else { - /* Just sync the buffer and give it back - * to the card. + /* CPU should not write to + * DMA_FROM_DEVICE-mapped area, + * so dma_sync_single_for_device() is + * not needed here. It would be required + * for DMA_BIDIRECTIONAL mapping if + * the memory was modified. */ - dma_sync_single_for_device(&cp->dev, - cp->rx_dma, - cp->rx_len, - DMA_FROM_DEVICE); give_rx_buf_to_card(cp); } } |