Commit | Line | Data |
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1da177e4 LT |
1 | USERSPACE MAD ACCESS |
2 | ||
3 | Device files | |
4 | ||
5 | Each port of each InfiniBand device has a "umad" device and an | |
6 | "issm" device attached. For example, a two-port HCA will have two | |
7 | umad devices and two issm devices, while a switch will have one | |
8 | device of each type (for switch port 0). | |
9 | ||
10 | Creating MAD agents | |
11 | ||
12 | A MAD agent can be created by filling in a struct ib_user_mad_reg_req | |
13 | and then calling the IB_USER_MAD_REGISTER_AGENT ioctl on a file | |
14 | descriptor for the appropriate device file. If the registration | |
15 | request succeeds, a 32-bit id will be returned in the structure. | |
16 | For example: | |
17 | ||
18 | struct ib_user_mad_reg_req req = { /* ... */ }; | |
19 | ret = ioctl(fd, IB_USER_MAD_REGISTER_AGENT, (char *) &req); | |
20 | if (!ret) | |
21 | my_agent = req.id; | |
22 | else | |
23 | perror("agent register"); | |
24 | ||
25 | Agents can be unregistered with the IB_USER_MAD_UNREGISTER_AGENT | |
26 | ioctl. Also, all agents registered through a file descriptor will | |
27 | be unregistered when the descriptor is closed. | |
28 | ||
29 | Receiving MADs | |
30 | ||
3f75dadd HR |
31 | MADs are received using read(). The receive side now supports |
32 | RMPP. The buffer passed to read() must be at least one | |
33 | struct ib_user_mad + 256 bytes. For example: | |
34 | ||
35 | If the buffer passed is not large enough to hold the received | |
36 | MAD (RMPP), the errno is set to ENOSPC and the length of the | |
37 | buffer needed is set in mad.length. | |
38 | ||
39 | Example for normal MAD (non RMPP) reads: | |
40 | struct ib_user_mad *mad; | |
41 | mad = malloc(sizeof *mad + 256); | |
42 | ret = read(fd, mad, sizeof *mad + 256); | |
43 | if (ret != sizeof mad + 256) { | |
44 | perror("read"); | |
45 | free(mad); | |
46 | } | |
47 | ||
48 | Example for RMPP reads: | |
49 | struct ib_user_mad *mad; | |
50 | mad = malloc(sizeof *mad + 256); | |
51 | ret = read(fd, mad, sizeof *mad + 256); | |
52 | if (ret == -ENOSPC)) { | |
53 | length = mad.length; | |
54 | free(mad); | |
55 | mad = malloc(sizeof *mad + length); | |
56 | ret = read(fd, mad, sizeof *mad + length); | |
57 | } | |
58 | if (ret < 0) { | |
1da177e4 | 59 | perror("read"); |
3f75dadd HR |
60 | free(mad); |
61 | } | |
1da177e4 LT |
62 | |
63 | In addition to the actual MAD contents, the other struct ib_user_mad | |
64 | fields will be filled in with information on the received MAD. For | |
65 | example, the remote LID will be in mad.lid. | |
66 | ||
67 | If a send times out, a receive will be generated with mad.status set | |
68 | to ETIMEDOUT. Otherwise when a MAD has been successfully received, | |
69 | mad.status will be 0. | |
70 | ||
71 | poll()/select() may be used to wait until a MAD can be read. | |
72 | ||
73 | Sending MADs | |
74 | ||
75 | MADs are sent using write(). The agent ID for sending should be | |
76 | filled into the id field of the MAD, the destination LID should be | |
3f75dadd HR |
77 | filled into the lid field, and so on. The send side does support |
78 | RMPP so arbitrary length MAD can be sent. For example: | |
79 | ||
80 | struct ib_user_mad *mad; | |
1da177e4 | 81 | |
3f75dadd | 82 | mad = malloc(sizeof *mad + mad_length); |
1da177e4 | 83 | |
3f75dadd | 84 | /* fill in mad->data */ |
1da177e4 | 85 | |
3f75dadd HR |
86 | mad->hdr.id = my_agent; /* req.id from agent registration */ |
87 | mad->hdr.lid = my_dest; /* in network byte order... */ | |
1da177e4 LT |
88 | /* etc. */ |
89 | ||
3f75dadd HR |
90 | ret = write(fd, &mad, sizeof *mad + mad_length); |
91 | if (ret != sizeof *mad + mad_length) | |
1da177e4 LT |
92 | perror("write"); |
93 | ||
bd8031b4 HR |
94 | Transaction IDs |
95 | ||
96 | Users of the umad devices can use the lower 32 bits of the | |
97 | transaction ID field (that is, the least significant half of the | |
98 | field in network byte order) in MADs being sent to match | |
99 | request/response pairs. The upper 32 bits are reserved for use by | |
100 | the kernel and will be overwritten before a MAD is sent. | |
101 | ||
2be8e3ee RD |
102 | P_Key Index Handling |
103 | ||
104 | The old ib_umad interface did not allow setting the P_Key index for | |
105 | MADs that are sent and did not provide a way for obtaining the P_Key | |
106 | index of received MADs. A new layout for struct ib_user_mad_hdr | |
107 | with a pkey_index member has been defined; however, to preserve | |
108 | binary compatibility with older applications, this new layout will | |
109 | not be used unless the IB_USER_MAD_ENABLE_PKEY ioctl is called | |
110 | before a file descriptor is used for anything else. | |
111 | ||
112 | In September 2008, the IB_USER_MAD_ABI_VERSION will be incremented | |
113 | to 6, the new layout of struct ib_user_mad_hdr will be used by | |
114 | default, and the IB_USER_MAD_ENABLE_PKEY ioctl will be removed. | |
115 | ||
1da177e4 LT |
116 | Setting IsSM Capability Bit |
117 | ||
118 | To set the IsSM capability bit for a port, simply open the | |
119 | corresponding issm device file. If the IsSM bit is already set, | |
120 | then the open call will block until the bit is cleared (or return | |
121 | immediately with errno set to EAGAIN if the O_NONBLOCK flag is | |
122 | passed to open()). The IsSM bit will be cleared when the issm file | |
123 | is closed. No read, write or other operations can be performed on | |
124 | the issm file. | |
125 | ||
126 | /dev files | |
127 | ||
128 | To create the appropriate character device files automatically with | |
129 | udev, a rule like | |
130 | ||
aa07a994 BVA |
131 | KERNEL=="umad*", NAME="infiniband/%k" |
132 | KERNEL=="issm*", NAME="infiniband/%k" | |
1da177e4 LT |
133 | |
134 | can be used. This will create device nodes named | |
135 | ||
136 | /dev/infiniband/umad0 | |
137 | /dev/infiniband/issm0 | |
138 | ||
139 | for the first port, and so on. The InfiniBand device and port | |
140 | associated with these devices can be determined from the files | |
141 | ||
142 | /sys/class/infiniband_mad/umad0/ibdev | |
143 | /sys/class/infiniband_mad/umad0/port | |
144 | ||
145 | and | |
146 | ||
147 | /sys/class/infiniband_mad/issm0/ibdev | |
148 | /sys/class/infiniband_mad/issm0/port |