Tribblix: 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)