From d7e02a931235de0779d44c6f8d211df0eca304b8 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Wed, 13 Mar 2019 18:45:21 +0100 Subject: dma-mapping: remove leftover NULL device support Most dma_map_ops implementations already had some issues with a NULL device, or did simply crash if one was fed to them. Now that we have cleaned up all the obvious offenders we can stop to pretend we support this mode. Signed-off-by: Christoph Hellwig --- Documentation/DMA-API-HOWTO.txt | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-) (limited to 'Documentation') diff --git a/Documentation/DMA-API-HOWTO.txt b/Documentation/DMA-API-HOWTO.txt index 1a721d0f35c8..0e98cf7466dd 100644 --- a/Documentation/DMA-API-HOWTO.txt +++ b/Documentation/DMA-API-HOWTO.txt @@ -365,13 +365,12 @@ __get_free_pages() (but takes size instead of a page order). If your driver needs regions sized smaller than a page, you may prefer using the dma_pool interface, described below. -The consistent DMA mapping interfaces, for non-NULL dev, will by -default return a DMA address which is 32-bit addressable. Even if the -device indicates (via DMA mask) that it may address the upper 32-bits, -consistent allocation will only return > 32-bit addresses for DMA if -the consistent DMA mask has been explicitly changed via -dma_set_coherent_mask(). This is true of the dma_pool interface as -well. +The consistent DMA mapping interfaces, will by default return a DMA address +which is 32-bit addressable. Even if the device indicates (via the DMA mask) +that it may address the upper 32-bits, consistent allocation will only +return > 32-bit addresses for DMA if the consistent DMA mask has been +explicitly changed via dma_set_coherent_mask(). This is true of the +dma_pool interface as well. dma_alloc_coherent() returns two values: the virtual address which you can use to access it from the CPU and dma_handle which you pass to the -- cgit