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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2019-05-09 08:40:55 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-05-09 08:40:55 -0700 |
| commit | ddab5337b23c99777d7cfb39c0f8efe536c17dff (patch) | |
| tree | fa2f935815614b474aca2e43afcddca69bda07fb /Documentation/DMA-API-HOWTO.txt | |
| parent | e57ccca1ba33e1d92cc3bbf8b6304a46948844b0 (diff) | |
| parent | 13bf5ced93775ffccb53527a9d862e023a9daa03 (diff) | |
| download | linux-ddab5337b23c99777d7cfb39c0f8efe536c17dff.tar.bz2 | |
Merge tag 'dma-mapping-5.2' of git://git.infradead.org/users/hch/dma-mapping
Pull DMA mapping updates from Christoph Hellwig:
- remove the already broken support for NULL dev arguments to the DMA
API calls
- Kconfig tidyups
* tag 'dma-mapping-5.2' of git://git.infradead.org/users/hch/dma-mapping:
dma-mapping: add a Kconfig symbol to indicate arch_dma_prep_coherent presence
dma-mapping: remove an unnecessary NULL check
x86/dma: Remove the x86_dma_fallback_dev hack
dma-mapping: remove leftover NULL device support
arm: use a dummy struct device for ISA DMA use of the DMA API
pxa3xx-gcu: pass struct device to dma_mmap_coherent
gbefb: switch to managed version of the DMA allocator
da8xx-fb: pass struct device to DMA API functions
parport_ip32: pass struct device to DMA API functions
dma: select GENERIC_ALLOCATOR for DMA_REMAP
Diffstat (limited to 'Documentation/DMA-API-HOWTO.txt')
| -rw-r--r-- | Documentation/DMA-API-HOWTO.txt | 13 |
1 files changed, 6 insertions, 7 deletions
diff --git a/Documentation/DMA-API-HOWTO.txt b/Documentation/DMA-API-HOWTO.txt index db48c6fd3162..cb712a02f59f 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 |