L4Re - L4 Runtime Environment
|
DMA Address Space. More...
Inherits L4::Kobject_0t< Derived, PROTO, S_DEMAND >.
Public Types | |
enum | Direction { Bidirectional, To_device, From_device, None } |
Direction of the DMA transfers. More... | |
enum | Attribute { No_sync } |
Attributes used for the memory region during the transfer. More... | |
enum | Space_attrib { Coherent, Phys_space } |
Attributes assigned to the DMA space when associated with a specific device. More... | |
typedef l4_uint64_t | Dma_addr |
Data type for DMA addresses. | |
typedef L4::Types::Flags< Attribute > | Attributes |
Attributes for DMA mappings. More... | |
typedef L4::Types::Flags< Space_attrib > | Space_attribs |
Attributes used when configuring the DMA space. | |
Public Member Functions | |
long | map (L4::Ipc::Cap< L4Re::Dataspace > src, l4_addr_t offset, L4::Ipc::In_out< l4_size_t *> size, Attributes attrs, Direction dir, Dma_addr *dma_addr) |
Map the given part of this data space into the DMA address space. More... | |
long | unmap (Dma_addr dma_addr, l4_size_t size, Attributes attrs, Direction dir) |
Unmap the given part of this data space from the DMA address space. More... | |
long | associate (L4::Ipc::Opt< L4::Ipc::Cap< L4::Task > > dma_task, Space_attribs attr) |
Associate a DMA task for a device to this Dma_space. More... | |
long | disassociate () |
Disassociate the DMA task from this Dma_space. More... | |
DMA Address Space.
A Dma_space represents the DMA address space of a device. Whenever a device needs direct access to parts of an L4Re::Dataspace, that part of the data space must be mapped to the DMA address space that is assigned to that device. After the DMA accesses to the memory are finished the memory must be unmapped from the device's DMA address space.
Mapping to a DMA address space, using map(), makes the given parts of the data space visible to the associated device at the returned DMA address. As long as the memory is mapped into a DMA space it is 'pinned' and cannot be subject to dynamic memory management such as swapping. Additionally, map() is responsible for the necessary syncing operations before the DMA.
unmap() is the reverse operation to map() and unmaps the given data-space part for the DMA address space. unmap() is responsible for the necessary sync operations after the DMA.
Attributes used for the memory region during the transfer.
Enumerator | |
---|---|
No_sync | Do not sync the memory hierarchy. When this flag is not set (default) the memory region shall be made coherent to the point-of-coherency of the device associated with this Dma_space. When using this attribute the client is responsible for syncing the memory hierarchy for DMA. This can either be done using the cache API or by another map() or unmap() operation of the same part of the data space (without the No_sync attribute). |
Attributes assigned to the DMA space when associated with a specific device.
Enumerator | |
---|---|
Coherent | The device is connected coherently with the cache. This means that the map() and unmap() do not need to sync CPU caches before and after DMA. |
Phys_space | The DMA space has no DMA task assigned and uses the CPUs physical memory. |
long L4Re::Dma_space::associate | ( | L4::Ipc::Opt< L4::Ipc::Cap< L4::Task > > | dma_task, |
Space_attribs | attr | ||
) |
Associate a DMA task for a device to this Dma_space.
[in] | dma_task | The DMA task used for the device that shall be associated with this DMA space. The dma_task might be an invalid capability when Phys_space is set in attr , in this case the CPUs physical memory is used as DMA address space. |
[in] | attr | Attributes for this DMA space. See Space_attrib. |
long L4Re::Dma_space::disassociate | ( | ) |
Disassociate the DMA task from this Dma_space.
long L4Re::Dma_space::map | ( | L4::Ipc::Cap< L4Re::Dataspace > | src, |
l4_addr_t | offset, | ||
L4::Ipc::In_out< l4_size_t *> | size, | ||
Attributes | attrs, | ||
Direction | dir, | ||
Dma_addr * | dma_addr | ||
) |
Map the given part of this data space into the DMA address space.
[in] | src | Source data space (that describes the memory). Caller needs write rights to the data space. |
[in] | offset | The offset (bytes) within src . |
[in,out] | size | The size (bytes) of the of the region to be mapped to for DMA, after successful mapping the size returned is the size mapped for DMA as single block, this size might be smaller than the original input size, in this case the caller might call map() again with a new offset and the remaining size. |
[in] | attrs | The attributes used for this DMA mapping (a combination of Dma_space::Attribute values). |
[in] | dir | The direction of the DMA transfer issued with this mapping. The same value must later be passed to unmap(). |
[out] | dma_addr | The DMA address to use for DMA with the associated device. |
long L4Re::Dma_space::unmap | ( | Dma_addr | dma_addr, |
l4_size_t | size, | ||
Attributes | attrs, | ||
Direction | dir | ||
) |
Unmap the given part of this data space from the DMA address space.
dma_addr | The DMA address (returned by Dma_space::map()). |
size | The size (bytes) of the memory region to unmap. |
attrs | The attributes for the unmap (currently none). |
dir | The direction of the finished DMA operation. |