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6 .TH DDI_DMA_REQ 9S "Oct 12, 2005"
7 .SH NAME
8 ddi_dma_req \- DMA Request structure
9 .SH SYNOPSIS
10 .LP
11 .nf
12 #include <sys/ddidmareq.h>
13 .fi
14
15 .SH INTERFACE LEVEL
16 .sp
17 .LP
18 Solaris DDI specific (Solaris DDI). This interface is obsolete.
19 .SH DESCRIPTION
20 .sp
21 .LP
22 A \fBddi_dma_req\fR structure describes a request for \fBDMA\fR resources. A
23 driver can use it to describe forms of allocations and ways to allocate
24 \fBDMA\fR resources for a \fBDMA\fR request.
25 .SH STRUCTURE MEMBERS
26 .sp
27 .in +2
28 .nf
29 ddi_dma_lim_t *dmar_limits; /* Caller's dma engine
30 constraints */
31 uint_t dmar_flags; /* Contains info for
32 mapping routines */
33 int (*dmar_fp)(caddr_t);/* Callback function */
34 caddr_t dmar_arg; /* Callback function's argument */
35 ddi_dma_obj_t dmar_object; /* Descrip. of object
36 to be mapped */
37 .fi
38 .in -2
39
40 .sp
41 .LP
42 For the definition of the \fBDMA\fR limits structure, which \fBdmar_limits\fR
43 points to, see \fBddi_dma_lim_sparc\fR(9S) or \fBddi_dma_lim_x86\fR(9S).
44 .sp
45 .LP
46 Valid values for \fBdmar_flags\fR are:
47 .sp
48 .in +2
49 .nf
50 DDI_DMA_WRITE /* Direction memory --> IO */
51 DDI_DMA_READ /* Direction IO --> memory */
52 DDI_DMA_RDWR /* Both read and write */
53 DDI_DMA_REDZONE /* Establish MMU redzone at end of mapping */
54 DDI_DMA_PARTIAL /* Partial mapping is allowed */
55 DDI_DMA_CONSISTENT /* Byte consistent access wanted */
56 DDI_DMA_SBUS_64BIT /* Use 64 bit capability on SBus */
57 .fi
58 .in -2
59
60 .sp
61 .LP
62 \fBDDI_DMA_WRITE\fR, \fBDDI_DMA_READ\fR, and \fBDDI_DMA_RDWR\fR describe the
63 intended direction of the \fBDMA \fRtransfer. Some implementations might
64 explicitly disallow \fBDDI_DMA_RDWR\fR.
65 .sp
66 .LP
67 \fBDDI_DMA_REDZONE\fR asks the system to establish a protected \fBred zone\fR
68 after the object. The \fBDMA\fR resource allocation functions do not guarantee
69 the success of this request, as some implementations might not have the
70 hardware ability to support it.
71 .sp
72 .LP
73 \fBDDI_DMA_PARTIAL\fR lets the system know that the caller can accept partial
74 mapping. That is, if the size of the object exceeds the resources available,
75 the system allocates only a portion of the object and returns status indicating
76 this partial allocation. At a later point, the caller can use
77 \fBddi_dma_curwin\fR(9F) and \fBddi_dma_movwin\fR(9F) to change the valid
78 portion of the object that has resources allocated.
79 .sp
80 .LP
81 \fBDDI_DMA_CONSISTENT\fR gives a hint to the system that the object should be
82 mapped for \fBbyte consistent\fR access. Normal data transfers usually use a
83 \fBstreaming\fR mode of operation. They start at a specific point, transfer a
84 fairly large amount of data sequentially, and then stop, usually on an aligned
85 boundary. Control mode data transfers for memory-resident device control blocks
86 (for example, Ethernet message descriptors) do not access memory in such a
87 sequential fashion. Instead, they tend to modify a few words or bytes, move
88 around and maybe modify a few more.
89 .sp
90 .LP
91 Many machine implementations make this non-sequential memory access difficult
92 to control in a generic and seamless fashion. Therefore, explicit
93 synchronization steps using \fBddi_dma_sync\fR(9F) or \fBddi_dma_free\fR(9F)
94 are required to make the view of a memory object shared between a \fBCPU \fRand
95 a \fBDMA\fR device consistent. However, proper use of the
96 \fBDDI_DMA_CONSISTENT\fR flag can create a condition in which a system will
97 pick resources in a way that makes these synchronization steps are as efficient
98 as possible.
99 .sp
100 .LP
101 \fBDDI_DMA_SBUS_64BIT\fR tells the system that the device can perform 64-bit
102 transfers on a 64-bit SBus. If the SBus does not support 64-bit data transfers,
103 data will be transferred in 32-bit mode.
104 .sp
105 .LP
106 The callback function specified by the member \fBdmar_fp\fR indicates how a
107 caller to one of the \fBDMA\fR resource allocation functions wants to deal with
108 the possibility of resources not being available. (See
109 \fBddi_dma_setup\fR(9F).) If \fBdmar_fp\fR is set to \fBDDI_DMA_DONTWAIT\fR,
110 then the caller does not care if the allocation fails, and can deal with an
111 allocation failure appropriately. Setting \fBdmar_fp\fR to \fBDDI_DMA_SLEEP\fR
112 indicates the caller wants to have the allocation routines wait for resources
113 to become available. If any other value is set, and a \fBDMA\fR resource
114 allocation fails, this value is assumed to be a function to call later, when
115 resources become available. When the specified function is called, it is passed
116 the value set in the structure member \fBdmar_arg\fR. The specified callback
117 function \fBmust\fR return either:
118 .sp
119 .ne 2
120 .na
121 \fB\fB0\fR\fR
122 .ad
123 .RS 5n
124 Indicating that it attempted to allocate a \fBDMA\fR resource but failed to do
125 so, again, in which case the callback function will be put back on a list to be
126 called again later.
127 .RE
128
129 .sp
130 .ne 2
131 .na
132 \fB\fB1\fR\fR
133 .ad
134 .RS 5n
135 Indicating either success at allocating \fBDMA\fR resources or that it no
136 longer wants to retry.
137 .RE
138
139 .sp
140 .LP
141 The callback function is called in interrupt context. Therefore, only system
142 functions and contexts that are accessible from interrupt context are
143 available. The callback function must take whatever steps necessary to protect
144 its critical resources, data structures, and queues.
145 .sp
146 .LP
147 It is possible that a call to \fBddi_dma_free\fR(9F), which frees \fBDMA\fR
148 resources, might cause a callback function to be called and, unless some care
149 is taken, an undesired recursion can occur. This can cause an undesired
150 recursive \fBmutex_enter\fR(9F), which makes the system panic.
151 .SS "dmar_object Structure"
152 .sp
153 .LP
154 The \fBdmar_object\fR member of the \fBddi_dma_req\fR structure is itself a
155 complex and extensible structure:
156 .sp
157 .in +2
158 .nf
159 uint_t dmao_size; /* size, in bytes, of the object */
160 ddi_dma_atyp_t dmao_type; /* type of object */
161 ddi_dma_aobj_t dmao_obj; /* the object described */
162 .fi
163 .in -2
164
165 .sp
166 .LP
167 The \fBdmao_size\fR element is the size, in bytes, of the object resources
168 allocated for \fBDMA\fR.
169 .sp
170 .LP
171 The \fBdmao_type\fR element selects the kind of object described by
172 \fBdmao_obj\fR. It can be set to \fBDMA_OTYP_VADDR\fR, indicating virtual
173 addresses.
174 .sp
175 .LP
176 The last element, \fBdmao_obj\fR, consists of the virtual address type:
177 .sp
178 .in +2
179 .nf
180 struct v_address virt_obj;
181 .fi
182 .in -2
183
184 .sp
185 .LP
186 It is specified as:
187 .sp
188 .in +2
189 .nf
190 struct v_address {
191 caddr_t v_addr; /* base virtual address */
192 struct as *v_as; /* pointer to address space */
193 void *v_priv; /* priv data for shadow I/O */
194 };
195 .fi
196 .in -2
197
198 .SH ATTRIBUTES
199 .sp
200 .LP
201 See \fBattributes\fR(5) for descriptions of the following attributes:
202 .sp
203
204 .sp
205 .TS
206 box;
207 c | c
208 l | l .
209 ATTRIBUTE TYPE ATTRIBUTE VALUE
210 _
211 Interface Stability Obsolete
212 .TE
213
214 .SH SEE ALSO
215 .sp
216 .LP
217 \fBddi_dma_addr_setup\fR(9F), \fBddi_dma_buf_setup\fR(9F),
218 \fBddi_dma_curwin\fR(9F), \fBddi_dma_free\fR(9F), \fBddi_dma_movwin\fR(9F),
219 \fBddi_dma_setup\fR(9F), \fBddi_dma_sync\fR(9F), \fBmutex\fR(9F)
220 .sp
221 .LP
222 \fIWriting Device Drivers\fR