1 MC_GETPROP(9E) Driver Entry Points MC_GETPROP(9E)
2
3 NAME
4 mc_getprop - get device properties
5
6 SYNOPSIS
7 #include <sys/mac_provider.h>
8
9 int
10 prefix_m_getprop(void *driver, const char *pr_name, mac_prop_id_t pr_num,
11 uint_t pr_valsize, void *pr_val);
12
13 INTERFACE LEVEL
14 illumos DDI specific
15
16 PARAMETERS
17 driver A pointer to the driver's private data that was passed in
18 via the m_pdata member of the mac_register(9S) structure to
19 the mac_register(9F) function.
20
21 pr_name A null-terminated string that contains the name of the
22 property.
23
24 pr_num A constant that is used to identify the property.
25
26 pr_valsize A value that indicates the size in bytes of pr_val.
27
28 pr_val A pointer to a pr_valsize byte buffer that can store the
29 property.
30
31 DESCRIPTION
32 The mc_getprop() entry point is used to obtain the value of a given
33 device's property and place it into pr_val.
34
35 When the mc_getprop() entry point is called, the driver needs to first
36 identify the property. The set of possible properties and their meaning
37 is listed in the PROPERTIES section of mac(9E). It should identify the
38 property based on the value of pr_num. Most drivers will use a switch
39 statement and for any property that it supports it should then check if
40 the value in pr_valsize is sufficient for the property, comparing it to
41 the minimum size listed for the property in mac(9E). If it is not, then
42 it should return an error. Otherwise, it should copy the property's
43 value into pr_val. When an unknown or unsupported property is
44 encountered, generally the default case of the switch statement, the
45 device driver should return an error.
46
47 The special property MAC_PROP_PRIVATE indicates that this is a device
48 driver specific private property. The device driver must then look at
49 the value of the pr_name argument and use strcmp(9F) on it, comparing it
50 to each of its private (bounded-size) properties to identify which one it
51 is.
52
53 At this time, private properties are limited to being string based
54 properties. If other types of property values are used, they will not be
55 rendered correctly by dladm(1M).
56
57 The device driver can access its device soft state by casting the device
58 pointer to the appropriate structure. As this may be called while other
59 operations are ongoing, the device driver should employ the appropriate
60 locking while reading the properties.
61
62 CONTEXT
63 The mc_getprop() function is generally called from kernel context.
64
65 RETURN VALUES
66 Upon successful completion, the device driver should have copied the
67 value of the property into pr_val and return 0. Otherwise, a positive
68 error should be returned to indicate failure.
69
70 EXAMPLES
71 The following example shows how a device driver might structure its
72 mc_getprop() entry point.
73
74 #include <sys/mac_provider.h>
75
76 /*
77 * Note, this example merely shows the structure of this function.
78 * Different devices will manage their state in different ways. Like other
79 * examples, this assumes that the device has state in a structure called
80 * example_t and that there is a lock which keeps track of that state.
81 */
82 static char *example_priv_props[] = {
83 "_rx_intr_throttle",
84 "_tx_intr_throttle",
85 NULL
86 };
87
88 static int
89 example_m_getprop_private(example_t *ep, const char *pr_name, uint_t pr_valsize,
90 void *pr_val)
91 {
92 uint32_t val;
93
94 ASSERT(MUTEX_HELD(&ep->ep_lock));
95 if (strcmp(pr_name, example_priv_props[0] == 0) {
96 val = ep->ep_rx_itr;
97 } else if (strcmp(pr_name, example_priv_props[1] == 0) {
98 val = ep->ep_tx_itr;
99 } else {
100 return (ENOTSUP);
101 }
102
103 /*
104 * Due to issues in the GLDv3, these must be returned as string
105 * properties.
106 */
107 if (snprintf(pr_val, pr_valsize, "%d", val) >= pr_valsize)
108 return (EOVERFLOW);
109
110 return (0);
111 }
112
113 static int
114 example_m_getprop(void *arg, const char *pr_name, mac_prop_id_t pr_num,
115 uint_t pr_valsize, void *pr_val)
116 {
117 int ret = 0;
118 uint64_t speed;
119 example_t *ep = arg;
120
121 mutex_enter(&ep->ep_lock);
122
123 /*
124 * This only handles a subset of the properties that exist on the
125 * system. A proper driver will need to handle more. See mac(9E) for a
126 * full property list.
127 */
128 switch (pr_num) {
129 case MAC_PROP_DUPLEX:
130 if (pr_valsize < sizeof (link_duplex_t)) {
131 ret = EOVERFLOW;
132 break;
133 }
134 bcopy(ep->ep_link_duplex, pr_val, sizeof (link_duplex_t));
135 case MAC_PROP_SPEED:
136 if (pr_valsize < sizeof (uint64_t)) {
137 ret = EOVERFLOW;
138 break;
139 }
140 /*
141 * The link speed is stored in Mbits/s in this driver and is
142 * expected in bits/s.
143 */
144 speed = ep->ep_link_speed * 1000000ULL;
145 bcopy(&speed, pr_val, sizeof (speed));
146 break;
147 case MAC_PROP_MTU:
148 if (pr_valsize < sizeof (uint32_t)) {
149 ret = EOVERFLOW;
150 break;
151 }
152 bcopy(&ep->ep_mtu, pr_val, sizeof (speed));
153 break;
154 case MAC_PROP_PRIVATE:
155 ret = example_m_getprop_private(ep, pr_name, pr_valsize,
156 pr_val);
157 break;
158 default:
159 ret = ENOTSUP;
160 break;
161 }
162
163 mutex_exit(&ep->ep_lock);
164
165 return (ret);
166 }
167
168 ERRORS
169 The device driver may return one of the following errors. While this
170 list is not intended to be exhaustive, it is recommended to use one of
171 these if possible.
172
173 ENOTSUP This error should be used whenever an unknown or
174 unsupported property is encountered.
175
176 EOVERFLOW This error should be used when pr_valsize is smaller
177 than the required size for a given value.
178
179 SEE ALSO
180 mac(9E), mac_register(9F), strcmp(9F), mac_register(9S)
181
182 illumos February 15, 2020 illumos