illumos: manual page: ddi_dma_buf_bind

DDI_DMA_BUF_BIND_HANDLE(9F) Kernel Functions for Drivers

NAME

ddi_dma_buf_bind_handle - binds a system buffer to a DMA handle

SYNOPSIS

#include <sys/ddi.h>
#include <sys/sunddi.h>

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);

INTERFACE LEVEL

illumos DDI specific (illumos DDI).

PARAMETERS

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. This
should be left as NULL in new callers.

ccountp
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 calling ddi_dma_ncookies(9F).

DESCRIPTION

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() 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) structure.

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.

RETURN VALUES

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.

CONTEXT

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.

NOTES

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).

January 18, 2020 DDI_DMA_BUF_BIND_HANDLE(9F)