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

Solaris DDI specific (Solaris 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(9F) 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_SUCESS);
    }

    /*
     * detach(9F) 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

See attributes(5) for descriptions of the following attributes:

See Also

attributes(5), ddi_intr_alloc(9F), ddi_intr_free(9F), ddi_intr_set_nreq(9F)

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.