ddi_dma_buf_bind_handle - binds a system buffer to a DMA handle
int ddi_dma_buf_bind_handle(ddi_dma_handle_t handle, struct buf *bp,
uint_t flags, int (*callback)(caddr_t), caddr_t
arg, ddi_dma_cookie_t *cookiep, uint_t *ccountp);
illumos DDI specific (illumos DDI).
A pointer to a system buffer structure (see
Valid flags include:
Transfer direction is from memory to I/O
Transfer direction is from I/O to memory
Both read and write
Establish an MMU redzone at end of the
Partial resource allocation
Nonsequential, random, and small block transfers.
Sequential, unidirectional, block-sized, and
The address of a function to call back later if resources
are not available now. The following special function addresses may also be
Wait until resources are available.
Do not wait until resources are available and do not
schedule a callback.
Argument to be passed to the callback function,
callback, if such a function is specified.
A pointer to the first ddi_dma_cookie(9S)
structure. This should be left as NULL
in new callers.
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
Upon a successful return, ccountp
points to a
value representing the number of cookies for this DMA
object. This can
be left as NULL
in new callers. The cookie count can be obtained by
ddi_dma_buf_bind_handle() allocates and associates a number
of DMA cookies with handle. To get the total number of
cookies, callers should use the ddi_dma_ncookies(9F) function. To get
all of the cookies, callers should use the ddi_dma_cookie_iter(9F) or
ddi_dma_cookie_get(9F) functions. Callers should pass NULL for
cookiep and ccountp. These values are required if using the
deprecated ddi_dma_nextcookie(9F) interface, in which case
cookiep is filled in with the first ddi_dma_cookie(9S)
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
These flags describe the intended direction of the
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
fields in the DMA
used to allocate the most effective hardware support for large
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
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.
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
. At a later point, the caller can use
to change the valid portion of the object for which
resources are allocated. If resources were allocated for only part of the
returns resources for the first
window. Even when DDI_DMA_PARTIAL
is set, the system may
decide to allocate resources for the entire object (less overhead) in which
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.
Successfully allocated resources for the entire
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.
Another I/O transaction is using the DMA
No resources are available at the present time.
The object cannot be reached by the device requesting the
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_unbind_handle(9F), buf(9S), ddi_dma_attr(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