diff options
Diffstat (limited to 'drivers/staging/vme/vme_api.txt')
| -rw-r--r-- | drivers/staging/vme/vme_api.txt | 27 |
1 files changed, 19 insertions, 8 deletions
diff --git a/drivers/staging/vme/vme_api.txt b/drivers/staging/vme/vme_api.txt index a5c1b1cd5fcc..a910a0c4388b 100644 --- a/drivers/staging/vme/vme_api.txt +++ b/drivers/staging/vme/vme_api.txt @@ -77,16 +77,21 @@ driver in question: struct vme_resource * vme_slave_request(struct device *dev, vme_address_t aspace, vme_cycle_t cycle); - struct vme_resource *vme_dma_request(struct device *dev); + struct vme_resource *vme_dma_request(struct device *dev, + vme_dma_route_t route); For slave windows these attributes are split into those of type 'vme_address_t' -and 'vme_cycle_t'. Master windows add a further set of attributes 'vme_cycle_t'. -These attributes are defined as bitmasks and as such any combination of the -attributes can be requested for a single window, the core will assign a window -that meets the requirements, returning a pointer of type vme_resource that -should be used to identify the allocated resource when it is used. If an -unallocated window fitting the requirements can not be found a NULL pointer will -be returned. +and 'vme_cycle_t'. Master windows add a further set of attributes +'vme_cycle_t'. These attributes are defined as bitmasks and as such any +combination of the attributes can be requested for a single window, the core +will assign a window that meets the requirements, returning a pointer of type +vme_resource that should be used to identify the allocated resource when it is +used. For DMA controllers, the request function requires the potential +direction of any transfers to be provided in the route attributes. This is +typically VME-to-MEM and/or MEM-to-VME, though some hardware can support +VME-to-VME and MEM-to-MEM transfers as well as test pattern generation. If an +unallocated window fitting the requirements can not be found a NULL pointer +will be returned. Functions are also provided to free window allocations once they are no longer required. These functions should be passed the pointer to the resource provided @@ -237,6 +242,12 @@ covered under "Transfer Attributes"): struct vme_dma_attr *src, struct vme_dma_attr *dest, size_t count); +NOTE: The detailed attributes of the transfers source and destination + are not checked until an entry is added to a DMA list, the request + for a DMA channel purely checks the directions in which the + controller is expected to transfer data. As a result it is + possible for this call to return an error, for example if the + source or destination is in an unsupported VME address space. Transfer Attributes ------------------- |