illumos: manual page: mc

MC_GETPROP(9E) Driver Entry Points MC_GETPROP(9E)

NAME

mc_getprop - get device properties

SYNOPSIS

#include <sys/mac_provider.h>

int
prefix_m_getprop(void *driver, const char *pr_name, mac_prop_id_t pr_num,
uint_t pr_valsize, void *pr_val);

INTERFACE LEVEL

illumos DDI specific

PARAMETERS

driver A pointer to the driver's private data that was passed in via
the m_pdata member of the mac_register(9S) structure to the
mac_register(9F) function.

pr_name A null-terminated string that contains the name of the
property.

pr_num A constant that is used to identify the property.

pr_valsize A value that indicates the size in bytes of pr_val.

pr_val A pointer to a pr_valsize byte buffer that can store the
property.

DESCRIPTION

The mc_getprop() entry point is used to obtain the value of a given
device's property and place it into pr_val.

When the mc_getprop() entry point is called, the driver needs to first
identify the property. The set of possible properties and their meaning is
listed in the PROPERTIES section of mac(9E). It should identify the
property based on the value of pr_num. Most drivers will use a switch
statement and for any property that it supports it should then check if the
value in pr_valsize is sufficient for the property, comparing it to the
minimum size listed for the property in mac(9E). If it is not, then it
should return an error. Otherwise, it should copy the property's value
into pr_val. When an unknown or unsupported property is encountered,
generally the default case of the switch statement, the device driver
should return an error.

The special property MAC_PROP_PRIVATE indicates that this is a device
driver specific private property. The device driver must then look at the
value of the pr_name argument and use strcmp(9F) on it, comparing it to
each of its private (bounded-size) properties to identify which one it is.

At this time, private properties are limited to being string based
properties. If other types of property values are used, they will not be
rendered correctly by dladm(8).

The device driver can access its device soft state by casting the device
pointer to the appropriate structure. As this may be called while other
operations are ongoing, the device driver should employ the appropriate
locking while reading the properties.

CONTEXT

The mc_getprop() function is generally called from kernel context.

RETURN VALUES

Upon successful completion, the device driver should have copied the value
of the property into pr_val and return 0. Otherwise, a positive error
should be returned to indicate failure.

EXAMPLES

The following example shows how a device driver might structure its
mc_getprop() entry point.

#include <sys/mac_provider.h>

/*
* Note, this example merely shows the structure of this function.
* Different devices will manage their state in different ways. Like other
* examples, this assumes that the device has state in a structure called
* example_t and that there is a lock which keeps track of that state.
*/
static char *example_priv_props[] = {
"_rx_intr_throttle",
"_tx_intr_throttle",
NULL
};

static int
example_m_getprop_private(example_t *ep, const char *pr_name, uint_t pr_valsize,
void *pr_val)
{
uint32_t val;

ASSERT(MUTEX_HELD(&ep->ep_lock));
if (strcmp(pr_name, example_priv_props[0] == 0) {
val = ep->ep_rx_itr;
} else if (strcmp(pr_name, example_priv_props[1] == 0) {
val = ep->ep_tx_itr;
} else {
return (ENOTSUP);
}

/*
* Due to issues in the GLDv3, these must be returned as string
* properties.
*/
if (snprintf(pr_val, pr_valsize, "%d", val) >= pr_valsize)
return (EOVERFLOW);

return (0);
}

static int
example_m_getprop(void *arg, const char *pr_name, mac_prop_id_t pr_num,
uint_t pr_valsize, void *pr_val)
{
int ret = 0;
uint64_t speed;
example_t *ep = arg;

mutex_enter(&ep->ep_lock);

/*
* This only handles a subset of the properties that exist on the
* system. A proper driver will need to handle more. See mac(9E) for a
* full property list.
*/
switch (pr_num) {
case MAC_PROP_DUPLEX:
if (pr_valsize < sizeof (link_duplex_t)) {
ret = EOVERFLOW;
break;
}
bcopy(ep->ep_link_duplex, pr_val, sizeof (link_duplex_t));
case MAC_PROP_SPEED:
if (pr_valsize < sizeof (uint64_t)) {
ret = EOVERFLOW;
break;
}
/*
* The link speed is stored in Mbits/s in this driver and is
* expected in bits/s.
*/
speed = ep->ep_link_speed * 1000000ULL;
bcopy(&speed, pr_val, sizeof (speed));
break;
case MAC_PROP_MTU:
if (pr_valsize < sizeof (uint32_t)) {
ret = EOVERFLOW;
break;
}
bcopy(&ep->ep_mtu, pr_val, sizeof (speed));
break;
case MAC_PROP_PRIVATE:
ret = example_m_getprop_private(ep, pr_name, pr_valsize,
pr_val);
break;
default:
ret = ENOTSUP;
break;
}

mutex_exit(&ep->ep_lock);

return (ret);
}

ERRORS

The device driver may return one of the following errors. While this list
is not intended to be exhaustive, it is recommended to use one of these if
possible.

ENOTSUP This error should be used whenever an unknown or
unsupported property is encountered.

EOVERFLOW This error should be used when pr_valsize is smaller
than the required size for a given value.