From 3f0fb4e85b3842a2606c647c0a66afe2073574b4 Mon Sep 17 00:00:00 2001 From: Michal Miroslaw Date: Tue, 26 Jul 2011 16:08:51 -0700 Subject: [PATCH] Documentation/DMA-API-HOWTO.txt: fix misleading example See: DMA-API.txt, part Id, DMA_FROM_DEVICE description. Signed-off-by: Michal Miroslaw Cc: FUJITA Tomonori Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/DMA-API-HOWTO.txt | 12 ++++++------ 1 file 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); } } -- 2.20.1