illumos: manual page: ddi_cb

DDI_CB_REGISTER(9F) Kernel Functions for Drivers DDI_CB_REGISTER(9F)

NAME

ddi_cb_register, ddi_cb_unregister - register and unregister a device
driver callback handler

SYNOPSIS

#include <sys/sunddi.h>

int ddi_cb_register(dev_info_t *dip, ddi_cb_flags_t flags,
ddi_cb_func_t cbfunc, void *arg1, void *arg2,
ddi_cb_handle_t * ret_hdlp);

int ddi_cb_unregister(ddi_cb_handle_t hdl);

INTERFACE LEVEL

illumos DDI specific (illumos DDI).

PARAMETERS

ddi_cb_register()

dip
Pointer to the dev_info structure.

flags
Flags to determine which callback events can be handled.

cbfunc
Callback handler function.

arg1
First argument to the callback handler.

arg2
Second (optional) argument to the callback handler.

ret_hdlp
Pointer to return a handle to the registered callback.

ddi_cb_unregister()

hdl
Handle to the registered callback handler that is to be
unregistered.

DESCRIPTION

The ddi_cb_register() function installs a callback handler which
processes various actions that require the driver's attention while it is
attached. The driver specifies which callback actions it can handle
through the flags parameter. With each relevant action, the specified
callback function passes the arg1 and arg2 arguments along with the
description of each callback event to the driver.

The ddi_cb_unregister() function removes a previously installed callback
handler and prevents future processing of actions.

The flags parameter consists of the following:

DDI_CB_FLAG_INTR
The device driver participates in interrupt resource
management. The device driver may receive additional
interrupt resources from the system, but only because
it can accept callback notices informing it when it
has more or less resources available. Callback
notices can occur at anytime after the driver is
attached. Interrupt availability varies based on the
overall needs of the system.

The cdfunc is a callback handler with the following prototype:

typedef int (*ddi_cb_func_t)(dev_info_t *dip,
ddi_cb_action_t action, void *cbarg,
void *arg1, void *arg2);

The cbfunc routine with the arguments dip, action, cbarg, arg1 and arg2
is called upon receipt of any callbacks for which the driver is
registered. The callback handler returns DDI_SUCCESS if the callback was
handled successfully, DDI_ENOTSUP if it received a callback action that
it did not know how to process, or DDI_FAILURE if it has an internal
failure while processing an action.

The action parameter can be one of the following:

DDI_CB_INTR_ADD
For interrupt resource management, the driver has
more available interrupts. The driver can allocate
more interrupt vectors and then set up more
interrupt handling functions by using
ddi_intr_alloc(9F).

DDI_CB_INTR_REMOVE
For interrupt resource management, the driver has
fewer available interrupts. The driver must
release any previously allocated interrupts in
excess of what is now available by using
ddi_intr_free(9F).

The cbarg parameter points to an action-specific argument. Each class of
registered actions specifies its own data structure that a callback
handler should dereference when it receives those actions.

The cbarg parameter is defined as an integer in the case of
DDI_CB_INTR_ADD and DDI_CB_INTR_REMOVE actions. The callback handler
should cast the cbarg parameter to an integer. The integer represents how
many interrupts have been added or removed from the total number
available to the device driver.

If a driver participates in interrupt resource management, it must
register a callback with the DDI_CB_FLAG_INTR flag. The driver then
receives the actions DDI_CB_INTR_ADD and DDI_CB_INTR_REMOVE whenever its
interrupt availability has changed. The callback handler should use the
interrupt functions ddi_intr_alloc(9F) and ddi_intr_free(9F) functions to
respond accordingly. A driver is not required to allocate all interrupts
that are available to it, but it is required to manage its allocations so
that it never uses more interrupts than are currently available.

RETURN VALUES

The ddi_cb_register() and ddi_cb_unregister() functions return:

DDI_SUCCESS
on success

DDI_EINVAL
An invalid parameter was given when registering a
callback handler, or an invalid handle was given when
unregistering.

DDI_EALREADY
An attempt was made to register a callback handler while
a previous registration still exists.

The cbfunc routine must return:

DDI_SUCCESS
on success

DDI_ENOTSUP
The device does not support the operation

DDI_FAILURE
Implementation specific failure

CONTEXT

These functions can be called from kernel, non-interrupt context.

EXAMPLES

Example 1: ddi_cb_register

/*
* attach(9E) routine.
*
* Creates soft state, registers callback handler, initializes
* hardware, and sets up interrupt handling for the driver.
*/
xx_attach(dev_info_t *dip, ddi_attach_cmd_t cmd)
{
xx_state_t *statep = NULL;
xx_intr_t *intrs = NULL;
ddi_intr_handle_t *hdls;
ddi_cb_handle_t cb_hdl;
int instance;
int type;
int types;
int nintrs;
int nactual;
int inum;

/* Get device instance */
instance = ddi_get_instance(dip);

switch (cmd) {
case DDI_ATTACH:

/* Get soft state */
if (ddi_soft_state_zalloc(state_list, instance) != 0)
return (DDI_FAILURE);
statep = ddi_get_soft_state(state_list, instance);
ddi_set_driver_private(dip, (caddr_t)statep);
statep->dip = dip;

/* Initialize hardware */
xx_initialize(statep);

/* Register callback handler */
if (ddi_cb_register(dip, DDI_CB_FLAG_INTR, xx_cbfunc,
statep, NULL, &cb_hdl) != 0) {
ddi_soft_state_free(state_list, instance);
return (DDI_FAILURE);
}
statep->cb_hdl = cb_hdl;

/* Select interrupt type */
ddi_intr_get_supported_types(dip, &types);
if (types & DDI_INTR_TYPE_MSIX) {
type = DDI_INTR_TYPE_MSIX;
} else if (types & DDI_INTR_TYPE_MSI) {
type = DDI_INTR_TYPE_MSI;
} else {
type = DDI_INTR_TYPE_FIXED;
}
statep->type = type;

/* Get number of supported interrupts */

ddi_intr_get_nintrs(dip, type, &nintrs);

/* Allocate interrupt handle array */
statep->hdls_size = nintrs * sizeof (ddi_intr_handle_t);
hdls = kmem_zalloc(statep->hdls_size, KMEM_SLEEP);

/* Allocate interrupt setup array */
statep->intrs_size = nintrs * sizeof (xx_intr_t);
statep->intrs = kmem_zalloc(statep->intrs_size, KMEM_SLEEP);

/* Allocate interrupt vectors */
ddi_intr_alloc(dip, hdls, type, 0, nintrs, &nactual, 0);
statep->nactual = nactual;

/* Configure interrupt handling */
xx_setup_interrupts(statep, nactual, statep->intrs);

/* Install and enable interrupt handlers */
for (inum = 0; inum < nactual; inum++) {
ddi_intr_add_handler(&statep->hdls[inum],
statep->intrs[inum].inthandler,
statep->intrs[inum].arg1,
statep->intrs[inum].arg2);
ddi_intr_enable(statep->hdls[inum]);
}

break;

case DDI_RESUME:

/* Get soft state */
statep = ddi_get_soft_state(state_list, instance);
if (statep == NULL)
return (DDI_FAILURE);

/* Resume hardware */
xx_resume(statep);

break;
}

return (DDI_SUCCESS);
}

/*
* detach(9E) routine.
*
* Stops the hardware, disables interrupt handling, unregisters
* a callback handler, and destroys the soft state for the driver.
*/
xx_detach(dev_info_t *dip, ddi_detach_cmd_t cmd)
{
xx_state_t *statep = NULL;
int instance;
int inum;

/* Get device instance */
instance = ddi_get_instance(dip);

switch (cmd) {
case DDI_DETACH:

/* Get soft state */
statep = ddi_get_soft_state(state_list, instance);
if (statep == NULL)
return (DDI_FAILURE);

/* Stop device */
xx_uninitialize(statep);

/* Disable and free interrupts */
for (inum = 0; inum < statep->nactual; inum++) {
ddi_intr_disable(statep->hdls[inum]);
ddi_intr_remove_handler(statep->hdls[inum]);
ddi_intr_free(statep->hdls[inum]);
}

/* Unregister callback handler */
ddi_cb_unregister(statep->cb_hdl);

/* Free interrupt handle array */
kmem_free(statep->hdls, statep->hdls_size);

/* Free interrupt setup array */
kmem_free(statep->intrs, statep->intrs_size);

/* Free soft state */
ddi_soft_state_free(state_list, instance);

break;

case DDI_SUSPEND:

/* Get soft state */
statep = ddi_get_soft_state(state_list, instance);
if (statep == NULL)
return (DDI_FAILURE);

/* Suspend hardware */
xx_quiesce(statep);

break;
}

return (DDI_SUCCESS);
}

/*
* (*ddi_cbfunc)() routine.
*
* Adapt interrupt usage when availability changes.
*/
int
xx_cbfunc(dev_info_t *dip, ddi_cb_action_t cbaction, void *cbarg,
void *arg1, void *arg2)
{
xx_state_t *statep = (xx_state_t *)arg1;
int count;
int inum;
int nactual;

switch (cbaction) {
case DDI_CB_INTR_ADD:
case DDI_CB_INTR_REMOVE:

/* Get change in availability */
count = (int)(uintptr_t)cbarg;

/* Suspend hardware */
xx_quiesce(statep);

/* Tear down previous interrupt handling */
for (inum = 0; inum < statep->nactual; inum++) {
ddi_intr_disable(statep->hdls[inum]);
ddi_intr_remove_handler(statep->hdls[inum]);
}

/* Adjust interrupt vector allocations */
if (cbaction == DDI_CB_INTR_ADD) {

/* Allocate additional interrupt vectors */
ddi_intr_alloc(dip, statep->hdls, statep->type,
statep->nactual, count, &nactual, 0);

/* Update actual count of available interrupts */
statep->nactual += nactual;

} else {

/* Free removed interrupt vectors */
for (inum = statep->nactual - count;
inum < statep->nactual; inum++) {
ddi_intr_free(statep->hdls[inum]);
}

/* Update actual count of available interrupts */
statep->nactual -= count;
}

/* Configure interrupt handling */
xx_setup_interrupts(statep, statep->nactual, statep->intrs);

/* Install and enable interrupt handlers */
for (inum = 0; inum < statep->nactual; inum++) {
ddi_intr_add_handler(&statep->hdls[inum],
statep->intrs[inum].inthandler,
statep->intrs[inum].arg1,
statep->intrs[inum].arg2);
ddi_intr_enable(statep->hdls[inum]);
}

/* Resume hardware */
xx_resume(statep);

break;

default:
return (DDI_ENOTSUP);
}

return (DDI_SUCCESS);
}

ATTRIBUTES

NOTES

Users of these interfaces that register for DDI_CB_FLAG_INTR become
participants in interrupt resource management. With that participation
comes a responsibility to properly adjust interrupt usage. In the case of
a DDI_CB_INTR_ADD action, the system guarantees that a driver can
allocate a total number of interrupt resources up to its new number of
available interrupts. The total number of interrupt resources is the sum
of all resources allocated by the function ddi_intr_alloc(9F), minus all
previously released by the function ddi_intr_free(9F). In the case of a
DDI_CB_INTR_REMOVE action, the driver might have more interrupts
allocated than are now currently available. It is necessary for the
driver to release the excess interrupts, or it will have a negative
impact on the interrupt availability for other drivers in the system.

A failure to release interrupts in response to a DDI_CB_INTR_REMOVE
callback generates the following warning on the system console:

WARNING: <driver><instance>: failed to release interrupts for
IRM (nintrs = ##, navail=##).

Participation in interrupt resource management ends when a driver uses
the ddi_cb_unregister() function to unregister its callback function. The
callback function must still operate properly until after the call to the
ddi_cb_unregister() function completes. If addinterrupts were given to
the driver because of its participation, then a final use of the callback
function occurs to release the additional interrupts. The call to the
ddi_cb_unregister() function blocks until the final use of the
registered callback function is finished.

January 30, 2009 DDI_CB_REGISTER(9F)