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Commit 3f0fb4e85b3842a2606c647c0a66afe2073574b4

Authored by Michal Miroslaw
Committed by Linus Torvalds
1 parent 91f6cdf86e
Exists in master and in 6 other branches imx_3.10.17_1.0.1_ga, imx_3.10.53_1.1.0_ga, imx_3.14.28_1.0.0_ga, smarc-imx_3.10.53_1.1.0_ga, smarc-imx_3.14.28_1.0.0_ga, smarc-l5.0.0_1.0.0-ga

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>

Showing 1 changed file with 6 additions and 6 deletions Side-by-side Diff

Documentation/DMA-API-HOWTO.txt
Diff comments   View file @ 3f0fb4e
... ... @@ -613,13 +613,13 @@
613 613 pass_to_upper_layers(cp->rx_buf);
614 614 make_and_setup_new_rx_buf(cp);
615 615 } else {
616   - /* Just sync the buffer and give it back
617   - * to the card.
  616 + /* CPU should not write to
  617 + * DMA_FROM_DEVICE-mapped area,
  618 + * so dma_sync_single_for_device() is
  619 + * not needed here. It would be required
  620 + * for DMA_BIDIRECTIONAL mapping if
  621 + * the memory was modified.
618 622 */
619   - dma_sync_single_for_device(&cp->dev,
620   - cp->rx_dma,
621   - cp->rx_len,
622   - DMA_FROM_DEVICE);
623 623 give_rx_buf_to_card(cp);
624 624 }
625 625 }