100 lines
3.1 KiB
Text
100 lines
3.1 KiB
Text
|
USERSPACE MAD ACCESS
|
||
|
|
|
||
|
|
Device files
|
||
|
|
|
||
|
|
Each port of each InfiniBand device has a "umad" device and an
|
||
|
|
"issm" device attached. For example, a two-port HCA will have two
|
||
|
|
umad devices and two issm devices, while a switch will have one
|
||
|
|
device of each type (for switch port 0).
|
||
|
|
|
||
|
|
Creating MAD agents
|
||
|
|
|
||
|
|
A MAD agent can be created by filling in a struct ib_user_mad_reg_req
|
||
|
|
and then calling the IB_USER_MAD_REGISTER_AGENT ioctl on a file
|
||
|
|
descriptor for the appropriate device file. If the registration
|
||
|
|
request succeeds, a 32-bit id will be returned in the structure.
|
||
|
|
For example:
|
||
|
|
|
||
|
|
struct ib_user_mad_reg_req req = { /* ... */ };
|
||
|
|
ret = ioctl(fd, IB_USER_MAD_REGISTER_AGENT, (char *) &req);
|
||
|
|
if (!ret)
|
||
|
|
my_agent = req.id;
|
||
|
|
else
|
||
|
|
perror("agent register");
|
||
|
|
|
||
|
|
Agents can be unregistered with the IB_USER_MAD_UNREGISTER_AGENT
|
||
|
|
ioctl. Also, all agents registered through a file descriptor will
|
||
|
|
be unregistered when the descriptor is closed.
|
||
|
|
|
||
|
|
Receiving MADs
|
||
|
|
|
||
|
|
MADs are received using read(). The buffer passed to read() must be
|
||
|
|
large enough to hold at least one struct ib_user_mad. For example:
|
||
|
|
|
||
|
|
struct ib_user_mad mad;
|
||
|
|
ret = read(fd, &mad, sizeof mad);
|
||
|
|
if (ret != sizeof mad)
|
||
|
|
perror("read");
|
||
|
|
|
||
|
|
In addition to the actual MAD contents, the other struct ib_user_mad
|
||
|
|
fields will be filled in with information on the received MAD. For
|
||
|
|
example, the remote LID will be in mad.lid.
|
||
|
|
|
||
|
|
If a send times out, a receive will be generated with mad.status set
|
||
|
|
to ETIMEDOUT. Otherwise when a MAD has been successfully received,
|
||
|
|
mad.status will be 0.
|
||
|
|
|
||
|
|
poll()/select() may be used to wait until a MAD can be read.
|
||
|
|
|
||
|
|
Sending MADs
|
||
|
|
|
||
|
|
MADs are sent using write(). The agent ID for sending should be
|
||
|
|
filled into the id field of the MAD, the destination LID should be
|
||
|
|
filled into the lid field, and so on. For example:
|
||
|
|
|
||
|
|
struct ib_user_mad mad;
|
||
|
|
|
||
|
|
/* fill in mad.data */
|
||
|
|
|
||
|
|
mad.id = my_agent; /* req.id from agent registration */
|
||
|
|
mad.lid = my_dest; /* in network byte order... */
|
||
|
|
/* etc. */
|
||
|
|
|
||
|
|
ret = write(fd, &mad, sizeof mad);
|
||
|
|
if (ret != sizeof mad)
|
||
|
|
perror("write");
|
||
|
|
|
||
|
|
Setting IsSM Capability Bit
|
||
|
|
|
||
|
|
To set the IsSM capability bit for a port, simply open the
|
||
|
|
corresponding issm device file. If the IsSM bit is already set,
|
||
|
|
then the open call will block until the bit is cleared (or return
|
||
|
|
immediately with errno set to EAGAIN if the O_NONBLOCK flag is
|
||
|
|
passed to open()). The IsSM bit will be cleared when the issm file
|
||
|
|
is closed. No read, write or other operations can be performed on
|
||
|
|
the issm file.
|
||
|
|
|
||
|
|
/dev files
|
||
|
|
|
||
|
|
To create the appropriate character device files automatically with
|
||
|
|
udev, a rule like
|
||
|
|
|
||
|
|
KERNEL="umad*", NAME="infiniband/%k"
|
||
|
|
KERNEL="issm*", NAME="infiniband/%k"
|
||
|
|
|
||
|
|
can be used. This will create device nodes named
|
||
|
|
|
||
|
|
/dev/infiniband/umad0
|
||
|
|
/dev/infiniband/issm0
|
||
|
|
|
||
|
|
for the first port, and so on. The InfiniBand device and port
|
||
|
|
associated with these devices can be determined from the files
|
||
|
|
|
||
|
|
/sys/class/infiniband_mad/umad0/ibdev
|
||
|
|
/sys/class/infiniband_mad/umad0/port
|
||
|
|
|
||
|
|
and
|
||
|
|
|
||
|
|
/sys/class/infiniband_mad/issm0/ibdev
|
||
|
|
/sys/class/infiniband_mad/issm0/port
|