ddi_dmae(9F) Kernel Functions for Drivers ddi_dmae(9F)
ddi_dmae, ddi_dmae_alloc, ddi_dmae_release, ddi_dmae_prog, ddi_dmae_disable, ddi_dmae_enable, ddi_dmae_stop, ddi_dmae_getcnt,
ddi_dmae_1stparty, ddi_dmae_getlim, ddi_dmae_getattr - system DMA engine functions
int ddi_dmae_alloc(dev_info_t *dip, int chnl, int (*callback) (caddr_t), caddr_t arg);
int ddi_dmae_release(dev_info_t *dip, int chnl);
int ddi_dmae_prog(dev_info_t *dip, struct ddi_dmae_req *dmaereqp, ddi_dma_cookie_t *cookiep, int chnl);
int ddi_dmae_disable(dev_info_t *dip, int chnl);
int ddi_dmae_enable(dev_info_t *dip, int chnl);
int ddi_dmae_stop(dev_info_t *dip, int chnl);
int ddi_dmae_getcnt(dev_info_t *dip, int chnl, int *countp);
int ddi_dmae_1stparty(dev_info_t *dip, int chnl);
int ddi_dmae_getlim(dev_info_t *dip, ddi_dma_lim_t *limitsp);
int ddi_dmae_getattr(dev_info_t *dip, ddi_dma_attr_t *attrp);
Solaris DDI specific (Solaris DDI). The ddi_dmae_getlim() interface, described below, is obsolete. Use ddi_dmae_getattr(), also described
below, to replace it.
dip A dev_info pointer that identifies the device.
chnl A DMA channel number. On ISA buses this number must be 0, 1, 2, 3, 5, 6, or 7.
callback The address of a function to call back later if resources are not currently available. 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, if specified.
dmaereqp A pointer to a DMA engine request structure. See ddi_dmae_req(9S).
cookiep A pointer to a ddi_dma_cookie(9S) object, obtained from ddi_dma_segtocookie(9F), which contains the address and count.
countp A pointer to an integer that will receive the count of the number of bytes not yet transferred upon completion of a DMA
limitsp A pointer to a DMA limit structure. See ddi_dma_lim_x86(9S).
attrp A pointer to a DMA attribute structure. See ddi_dma_attr(9S).
There are three possible ways that a device can perform DMA engine functions:
Bus master DMA
If the device is capable of acting as a true bus master, then the driver should program the device's DMA registers directly and not
make use of the DMA engine functions described here. The driver should obtain the DMA address and count from ddi_dma_segtocookie(9F).
See ddi_dma_cookie(9S) for a description of a DMA cookie.
This method uses the system DMA engine that is resident on the main system board. In this model, the device cooperates with the sys-
tem's DMA engine to effect the data transfers between the device and memory. The driver uses the functions documented here, except
ddi_dmae_1stparty(), to initialize and program the DMA engine. For each DMA data transfer, the driver programs the DMA engine and then
gives the device a command to initiate the transfer in cooperation with that engine.
Using this method, the device uses its own DMA bus cycles, but requires a channel from the system's DMA engine. After allocating the
DMA channel, the ddi_dmae_1stparty() function may be used to perform whatever configuration is necessary to enable this mode.
The ddi_dmae_alloc() function is used to acquire a DMA channel of the system DMA engine. ddi_dmae_alloc() allows only one device at a time
to have a particular DMA channel allocated. It must be called prior to any other system DMA engine function on a channel. If the device
allows the channel to be shared with other devices, it must be freed using ddi_dmae_release() after completion of the DMA operation. In any
case, the channel must be released before the driver successfully detaches. See detach(9E). No other driver may acquire the DMA channel
until it is released.
If the requested channel is not immediately available, the value of callback determines what action will be taken. If the value of callback
is DDI_DMA_DONTWAIT, ddi_dmae_alloc() will return immediately. The value DDI_DMA_SLEEP will cause the thread to sleep and not return until
the channel has been acquired. Any other value is assumed to be a callback function address. In that case, ddi_dmae_alloc() returns immedi-
ately, and when resources might have become available, the callback function is called (with the argument arg) from interrupt context. When
the callback function is called, it should attempt to allocate the DMA channel again. If it succeeds or no longer needs the channel, it
must return the value DDI_DMA_CALLBACK_DONE. If it tries to allocate the channel but fails to do so, it must return the value DDI_DMA_CALL-
BACK_RUNOUT. In this case, the callback function is put back on a list to be called again later.
The ddi_dmae_prog() function programs the DMA channel for a DMA transfer. The ddi_dmae_req structure contains all the information necessary
to set up the channel, except for the memory address and count. Once the channel has been programmed, subsequent calls to ddi_dmae_prog()
may specify a value of NULL for dmaereqp if no changes to the programming are required other than the address and count values. It disables
the channel prior to setup, and enables the channel before returning. The DMA address and count are specified by passing ddi_dmae_prog() a
cookie obtained from ddi_dma_segtocookie(9F). Other DMA engine parameters are specified by the DMA engine request structure passed in
through dmaereqp. The fields of that structure are documented in ddi_dmae_req(9S).
Before using ddi_dmae_prog(), you must allocate system DMA resources using DMA setup functions such as ddi_dma_buf_setup(9F). ddi_dma_seg-
tocookie(9F) can then be used to retrieve a cookie which contains the address and count. Then this cookie is passed to ddi_dmae_prog().
The ddi_dmae_disable() function disables the DMA channel so that it no longer responds to a device's DMA service requests.
The ddi_dmae_enable() function enables the DMA channel for operation. This may be used to re-enable the channel after a call to
ddi_dmae_disable(). The channel is automatically enabled after successful programming by ddi_dmae_prog().
The ddi_dmae_stop() function disables the channel and terminates any active operation.
The ddi_dmae_getcnt() function examines the count register of the DMA channel and sets *countp to the number of bytes remaining to be
transferred. The channel is assumed to be stopped.
In the case of ISA buses, ddi_dmae_1stparty() configures a channel in the system's DMA engine to operate in a ``slave'' (``cascade'')
When operating in ddi_dmae_1stparty() mode, the DMA channel must first be allocated using ddi_dmae_alloc() and then configured using
ddi_dmae_1stparty(). The driver then programs the device to perform the I/O, including the necessary DMA address and count values obtained
Note that this function is obsolete. Use ddi_dmae_getattr(), described below, instead.
The ddi_dmae_getlim() function fills in the DMA limit structure, pointed to by limitsp, with the DMA limits of the system DMA engine. Driv-
ers for devices that perform their own bus mastering or use first-party DMA must create and initialize their own DMA limit structures; they
should not use ddi_dmae_getlim(). The DMA limit structure must be passed to the DMA setup routines so that they will know how to break the
DMA request into windows and segments (see ddi_dma_nextseg(9F) and ddi_dma_nextwin(9F)). If the device has any particular restrictions on
transfer size or granularity (such as the size of disk sector), the driver should further restrict the values in the structure members
before passing them to the DMA setup routines. The driver must not relax any of the restrictions embodied in the structure after it is
filled in by ddi_dmae_getlim(). After calling ddi_dmae_getlim(), a driver must examine, and possibly set, the size of the DMA engine's
scatter/gather list to determine whether DMA chaining will be used. See ddi_dma_lim_x86(9S) and ddi_dmae_req(9S) for additional information
on scatter/gather DMA.
The ddi_dmae_getattr() function fills in the DMA attribute structure, pointed to by attrp, with the DMA attributes of the system DMA
engine. Drivers for devices that perform their own bus mastering or use first-party DMA must create and initialize their own DMA attribute
structures; they should not use ddi_dmae_getattr(). The DMA attribute structure must be passed to the DMA resource allocation functions to
provide the information necessary to break the DMA request into DMA windows and DMA cookies. See ddi_dma_nextcookie(9F) and
DDI_SUCCESS Upon success, for all of these routines.
DDI_FAILURE May be returned due to invalid arguments.
DDI_DMA_NORESOURCES May be returned by ddi_dmae_alloc() if the requested resources are not available and the value of dmae_waitfp is
If ddi_dmae_alloc() is called from interrupt context, then its dmae_waitfp argument and the callback function must not have the value
DDI_DMA_SLEEP. Otherwise, all these routines may be called from user or interrupt context.
See attributes(5) for descriptions of the following attributes:
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|Architecture |x86 |
isa(4), attributes(5), ddi_dma_buf_setup(9F), ddi_dma_getwin(9F), ddi_dma_nextcookie(9F), ddi_dma_nextseg(9F), ddi_dma_nextwin(9F),
ddi_dma_segtocookie(9F), ddi_dma_setup(9F), ddi_dma_attr(9S), ddi_dma_cookie(9S), ddi_dma_lim_x86(9S), ddi_dma_req(9S), ddi_dmae_req(9S)
SunOS 5.10 18 Nov 2004 ddi_dmae(9F)