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2 .\" Copyright 2014 Garrett D'Amore <garrett@damore.org>
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7 .TH DDI_CHECK_ACC_HANDLE 9F "May 24, 2014"
8 .SH NAME
9 ddi_check_acc_handle, ddi_check_dma_handle \- Check data access and DMA handles
10 .SH SYNOPSIS
11 .LP
12 .nf
13 #include <sys/ddi.h>
14 #include <sys/sunddi.h>
15
16
17
18 \fBint\fR \fBddi_check_acc_handle\fR(\fBddi_acc_handle_t\fR \fI acc_handle\fR );
19 .fi
20
21 .LP
22 .nf
23 \fBint\fR \fBddi_check_dma_handle\fR(\fBddi_dma_handle_t\fR \fIdma_handle\fR );
24 .fi
25
26 .SH INTERFACE LEVEL
27 .sp
28 .LP
29 Solaris DDI specific (Solaris DDI)
30 .SH PARAMETERS
31 .sp
32 .ne 2
33 .na
34 \fB\fIacc_handle\fR \fR
35 .ad
36 .RS 15n
37 Data access handle obtained from a previous call to
38 \fBddi_regs_map_setup\fR(9F), \fBddi_dma_mem_alloc\fR(9F), or similar function.
39 .RE
40
41 .sp
42 .ne 2
43 .na
44 \fB\fIdma_handle\fR \fR
45 .ad
46 .RS 15n
47 DMA handle obtained from \fBddi_dma_alloc_handle\fP(9F).
48 .RE
49
50 .SH DESCRIPTION
51 .sp
52 .LP
53 The \fBddi_check_acc_handle()\fR\fB and ddi_check_dma_handle()\fR functions
54 check for faults that can interfere with communication between a driver and the
55 device it controls. Each function checks a single handle of a specific type and
56 returns a status value indicating whether faults affecting the resource mapped
57 by the supplied handle have been detected.
58 .sp
59 .LP
60 If a fault is indicated when checking a data access handle, this implies that
61 the driver is no longer able to access the mapped registers or memory using
62 programmed I/O through that handle. Typically, this might occur after the
63 device has failed to respond to an I/O access (for example, has incurred a bus
64 error or timed out). The effect of programmed I/O accesses made after this
65 happens is undefined; for example, read accesses (for example,
66 \fBddi_get8\fR(9F)) may return random values, and write accesses (for example,
67 \fBddi_put8\fR(9F)) may or may not have any effect. This type of fault is
68 normally fatal to the operation of the device, and the driver should report it
69 via \fBddi_dev_report_fault\fR(9F) specifying \fBDDI_SERVICE_LOST\fR for the
70 impact, and \fBDDI_DATAPATH_FAULT\fR for the location.
71 .sp
72 .LP
73 If a fault is indicated when checking a DMA handle, it implies that a fault has
74 been detected that has (or will) affect DMA transactions between the device and
75 the memory currently bound to the handle (or most recently bound, if the handle
76 is currently unbound). Possible causes include the failure of a component in
77 the DMA data path, or an attempt by the device to make an invalid DMA access.
78 The driver may be able to continue by falling back to a non-DMA mode of
79 operation, but in general, DMA faults are non-recoverable. The contents of the
80 memory currently (or previously) bound to the handle should be regarded as
81 indeterminate. The fault indication associated with the current transaction is
82 lost once the handle is (re-)bound, but because the fault may persist, future
83 DMA operations may not succeed.
84 .sp
85 .LP
86 Note that some implementations cannot detect all types of failure. If a fault
87 is not indicated, this does not constitute a guarantee that communication is
88 possible. However, if a check fails, this is a positive indication that a
89 problem \fBdoes\fR exist with respect to communication using that handle.
90 .SH RETURN VALUES
91 .sp
92 .LP
93 The \fBddi_check_acc_handle()\fR and \fBddi_check_dma_handle()\fR functions
94 return \fBDDI_SUCCESS\fR if no faults affecting the supplied handle are
95 detected and \fBDDI_FAILURE\fR if any fault affecting the supplied handle is
96 detected.
97 .SH EXAMPLES
98 .sp
99 .in +2
100 .nf
101 static int
102 xxattach(dev_info_t *dip, ddi_attach_cmd_t cmd)
103 {
104 \&...
105 /* This driver uses only a single register-access handle */
106 status = ddi_regs_map_setup(dip, REGSET_ZERO, ®addr,
107 0, 0, , &acc_attrs, &acc_hdl);
108 if (status != DDI_SUCCESS)
109 return (DDI_FAILURE);
110 \&...
111 }
112
113 static int
114 xxread(dev_t dev, struct uio *uio_p, cred_t *cred_p)
115 {
116 \&...
117 if (ddi_check_acc_handle(acc_hdl) != DDI_SUCCESS) {
118 ddi_dev_report_fault(dip, DDI_SERVICE_LOST,
119 DDI_DATAPATH_FAULT, "register access fault during read");
120 return (EIO);
121 }
122 \&...
123 .fi
124 .in -2
125
126 .SH CONTEXT
127 .sp
128 .LP
129 The \fBddi_check_acc_handle()\fR and \fBddi_check_dma_handle()\fR functions may
130 be called from user, kernel, or interrupt context.
131 .SH SEE ALSO
132 .sp
133 .LP
134 \fBddi_regs_map_setup\fR(9F), \fBddi_dma_alloc_handle\fR(9F),
135 \fBddi_dev_report_fault\fR(9F), \fBddi_get8\fR(9F), \fBddi_put8\fR(9F)