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Commit b2fb3664 authored by Mitchel Humpherys's avatar Mitchel Humpherys Committed by Will Deacon
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common: DMA-mapping: add DMA_ATTR_PRIVILEGED attribute 



This patch adds the DMA_ATTR_PRIVILEGED attribute to the DMA-mapping
subsystem.

Some advanced peripherals such as remote processors and GPUs perform
accesses to DMA buffers in both privileged "supervisor" and unprivileged
"user" modes.  This attribute is used to indicate to the DMA-mapping
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).

Cc: linux-doc@vger.kernel.org
Reviewed-by: default avatarRobin Murphy <robin.murphy@arm.com>
Tested-by: default avatarRobin Murphy <robin.murphy@arm.com>
Acked-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarMitchel Humpherys <mitchelh@codeaurora.org>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent 5baf1e9d

Documentation/DMA-attributes.txt

+10 −0
Original line number Diff line number Diff line
@@ -143,3 +143,13 @@ So, this provides a way for drivers to avoid those error messages on calls 
where allocation failures are not a problem, and shouldn't bother the logs.



NOTE: At the moment DMA_ATTR_NO_WARN is only implemented on PowerPC.



DMA_ATTR_PRIVILEGED

------------------------------



Some advanced peripherals such as remote processors and GPUs perform

accesses to DMA buffers in both privileged "supervisor" and unprivileged

"user" modes.  This attribute is used to indicate to the DMA-mapping

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).

include/linux/dma-mapping.h

+7 −0
Original line number Diff line number Diff line
@@ -62,6 +62,13 @@ 
 */

#define DMA_ATTR_NO_WARN	(1UL << 8)



/*

 * DMA_ATTR_PRIVILEGED: used to indicate that the buffer is fully

 * accessible at an elevated privilege level (and ideally inaccessible or

 * at least read-only at lesser-privileged levels).

 */

#define DMA_ATTR_PRIVILEGED		(1UL << 9)



/*

 * 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.  A CPU cannot