From: Petr Tesarik <petr.tesarik.ext@xxxxxxxxxx> Introduce a DMA attribute to tell the DMA-mapping subsystem that the operation is allowed to sleep. This patch merely adds the flag, but it does not do anything at the moment. Signed-off-by: Petr Tesarik <petr.tesarik.ext@xxxxxxxxxx> --- Documentation/core-api/dma-attributes.rst | 10 ++++++++++ include/linux/dma-mapping.h | 6 ++++++ 2 files changed, 16 insertions(+) diff --git a/Documentation/core-api/dma-attributes.rst b/Documentation/core-api/dma-attributes.rst index 1887d92e8e92..9ce00926455f 100644 --- a/Documentation/core-api/dma-attributes.rst +++ b/Documentation/core-api/dma-attributes.rst @@ -130,3 +130,13 @@ accesses to DMA buffers in both privileged "supervisor" and unprivileged subsystem that the buffer is fully accessible at the elevated privilege level (and ideally inaccessible or at least read-only at the lesser-privileged levels). + +DMA_ATTR_MAY_SLEEP +------------------ + +This tells the DMA-mapping subsystem that it is allowed to sleep. For example, +if mapping needs a bounce buffer, software IO TLB may use CMA for the +allocation if this flag is given. + +This attribute is not used for dma_alloc\* functions. Instead, the provided +GFP flags are used to determine whether the allocation may sleep. diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h index 0ee20b764000..7a75c503ac38 100644 --- a/include/linux/dma-mapping.h +++ b/include/linux/dma-mapping.h @@ -61,6 +61,12 @@ */ #define DMA_ATTR_PRIVILEGED (1UL << 9) +/* + * DMA_ATTR_MAY_SLEEP: This tells the DMA-mapping subsystem that it is allowed + * to sleep. + */ +#define DMA_ATTR_MAY_SLEEP (1UL << 10) + /* * A dma_addr_t can hold any valid DMA or bus address for the platform. It can * be given to a device to use as a DMA source or target. It is specific to a -- 2.25.1
