Solaris DDI specific (Solaris DDI).

handle

The DMA handle previously allocated by a call to ddi_dma_alloc_handle(9F).

bp

A pointer to a system buffer structure (see buf(9S)).

flags

Valid flags include:

DDI_DMA_WRITE

Transfer direction is from memory to I/O

DDI_DMA_READ

Transfer direction is from I/O to memory

DDI_DMA_RDWR

Both read and write

DDI_DMA_REDZONE

Establish an MMU redzone at end of the object.

DDI_DMA_PARTIAL

Partial resource allocation

DDI_DMA_CONSISTENT

Nonsequential, random, and small block transfers.

DDI_DMA_STREAMING

Sequential, unidirectional, block-sized, and block-aligned transfers.

callback

The address of a function to call back later if resources are not available now. The following special function addresses may also be used.

DDI_DMA_SLEEP

Wait until resources are available.

DDI_DMA_DONTWAIT

Do not wait until resources are available and do not schedule a callback.

arg

Argument to be passed to the callback function, callback, if such a function is specified.

cookiep

A pointer to the first ddi_dma_cookie(9S) structure.

ccountp

Upon a successful return, ccountp points to a value representing the number of cookies for this DMA object.

ddi_dma_buf_bind_handle() allocates DMA resources for a system buffer such that a device can perform DMA to or from the buffer. DMA resources are allocated considering the device's DMA attributes as expressed by ddi_dma_attr(9S) (see ddi_dma_alloc_handle(9F)).

ddi_dma_buf_bind_handle() fills in the first DMA tocookie pointed to by cookiep with the appropriate address, length, and bus type. *ccountp is set to the number of DMA cookies representing this DMA object. Subsequent DMA cookies must be retrieved by calling ddi_dma_nextcookie(9F) *countp-1 times.

When a DMA transfer completes, the driver should free up system DMA resources by calling ddi_dma_unbind_handle(9F).

The flags argument contains information for mapping routines.

DDI_DMA_WRITE, DDI_DMA_READ, DDI_DMA_RDWR

These flags describe the intended direction of the DMA transfer.

DDI_DMA_STREAMING

This flag should be set if the device is doing sequential, unidirectional, block-sized, and block-aligned transfers to or from memory. The alignment and padding constraints specified by the minxfer and burstsizes fields in the DMA attribute structure, ddi_dma_attr(9S) (see ddi_dma_alloc_handle(9F)) is used to allocate the most effective hardware support for large transfers.

DDI_DMA_CONSISTENT

This flag should be set if the device accesses memory randomly, or if synchronization steps using ddi_dma_sync(9F) need to be as efficient as possible. I/O parameter blocks used for communication between a device and a driver should be allocated using DDI_DMA_CONSISTENT.

DDI_DMA_REDZONE

If this flag is set, the system attempts to establish a protected red zone after the object. The DMA resource allocation functions do not guarantee the success of this request as some implementations may not have the hardware ability to support a red zone.

DDI_DMA_PARTIAL

Setting this flag indicates the caller can accept resources for part of the object. That is, if the size of the object exceeds the resources available, only resources for a portion of the object are allocated. The system indicates this condition returning status DDI_DMA_PARTIAL_MAP. At a later point, the caller can use ddi_dma_getwin(9F) to change the valid portion of the object for which resources are allocated. If resources were allocated for only part of the object, ddi_dma_addr_bind_handle() returns resources for the first DMA window. Even when DDI_DMA_PARTIAL is set, the system may decide to allocate resources for the entire object (less overhead) in which case DDI_DMA_MAPPED is returned.

The callback function, callback, indicates how a caller wants to handle the possibility of resources not being available. If callback is set to DDI_DMA_DONTWAIT, the caller does not care if the allocation fails, and can handle an allocation failure appropriately. If callback is set to DDI_DMA_SLEEP, the caller wishes to have the allocation routines wait for resources to become available. If any other value is set, and a DMA resource allocation fails, this value is assumed to be the address of a function to call at a later time when resources may become available. When the specified function is called, it is passed arg as an argument. The specified callback function must return either DDI_DMA_CALLBACK_RUNOUT or DDI_DMA_CALLBACK_DONE. DDI_DMA_CALLBACK_RUNOUT indicates that the callback function attempted to allocate DMA resources but failed to do so. In this case the callback function is put back on a list to be called again later. DDI_DMA_CALLBACK_DONE indicates either a successful allocation of DMA resources or that the driver no longer wishes to retry.

The callback function is called in interrupt context. Therefore, only system functions accessible from interrupt context are be available. The callback function must take whatever steps necessary to protect its critical resources, data structures, queues, etc.

ddi_dma_buf_bind_handle() returns:

DDI_DMA_MAPPED

Successfully allocated resources for the entire object.

DDI_DMA_PARTIAL_MAP

Successfully allocated resources for a part of the object. This is acceptable when partial transfers are permitted by setting the DDI_DMA_PARTIAL flag in flags.

DDI_DMA_INUSE

Another I/O transaction is using the DMA handle.

DDI_DMA_NORESOURCES

No resources are available at the present time.

DDI_DMA_NOMAPPING

The object cannot be reached by the device requesting the resources.

DDI_DMA_TOOBIG

The object is too big. A request of this size can never be satisfied on this particular system. The maximum size varies depending on machine and configuration.

ddi_dma_buf_bind_handle() can be called from user, kernel, or interrupt context, except when callback is set to DDI_DMA_SLEEP, in which case it can be called from user or kernel context only.

ddi_dma_addr_bind_handle(9F), ddi_dma_alloc_handle(9F), ddi_dma_free_handle(9F), ddi_dma_getwin(9F), ddi_dma_nextcookie(9F), ddi_dma_sync(9F), ddi_dma_unbind_handle(9F), buf(9S), ddi_dma_attr(9S), ddi_dma_cookie(9S)

Writing Device Drivers

If the driver permits partial mapping with the DDI_DMA_PARTIAL flag, the number of cookies in each window may exceed the size of the device's scatter/gather list as specified in the dma_attr_sgllen field in the ddi_dma_attr(9S) structure. In this case, each set of cookies comprising a DMA window will satisfy the DMA attributes as described in the ddi_dma_attr(9S) structure in all aspects. The driver should set up its DMA engine and perform one transfer for each set of cookies sufficient for its scatter/gather list, up to the number of cookies for this window, before advancing to the next window using ddi_dma_getwin(9F).