man pages section 9: DDI and DKI Kernel Functions

ddi_intr_dup_handler(9F)

Name

ddi_intr_dup_handler– reuse interrupt handler and arguments for MSI-X interrupts

Synopsis

#include <sys/types.h>
#include <sys/conf.h>
#include <sys/ddi.h>
#include <sys/sunddi.h>

int ddi_intr_dup_handler(ddi_intr_handle_t primary, int vector, 
     ddi_intr_handle_t *new);

Interface Level

Solaris DDI specific (Solaris DDI).

Parameters

primary: Original DDI interrupt handle
vector: Interrupt number to duplicate
new: Pointer to new DDI interrupt handle

Description

The ddi_intr_dup_handler() function is a feature for MSI-X interrupts that allows an unallocated interrupt vector of a device to use a previously initialized or added primary MSI-X interrupt vector in order to share the same vector address, vector data, interrupt handler, and handler arguments. This feature allows a driver to alias the resources provided by the Solaris Operating System to the unallocated interrupt vectors on an associated device. For example, if 2 MSI-X interrupts were allocated to a driver and 32 interrupts were supported on the device, the driver could alias the 2 interrupts it received to the 30 remaining on the device.

The ddi_intr_dup_handler() function must be called after the primary interrupt handle has been added to the system or enabled by ddi_intr_add_handler(9F) and ddi_intr_enable(9F) calls, respectively. If successful, the function returns the new interrupt handle for a given vector in the new argument passed to the function. The new interrupt handle must not have been previously allocated with ddi_intr_alloc(9F). Otherwise, the ddi_intr_dup_handler() call will fail.

The only supported calls on dup-ed interrupt handles are ddi_intr_set_mask(9F), ddi_intr_clr_mask(9F), ddi_intr_get_pending(9F), ddi_intr_enable(9F), ddi_intr_disable(9F), and ddi_intr_free(9F).

A call to ddi_intr_dup_handler() does not imply that the interrupt source is automatically enabled. Initially, the dup-ed handle is in the disabled state and must be enabled before it can be used by calling ddi_intr_enable(). Likewise, ddi_intr_disable() must be called to disable the enabled dup-ed interrupt source.

A dup-ed interrupt is removed by calling ddi_intr_free() after it has been disabled. The ddi_intr_remove_handler(9F) call is not required for a dup-ed handle.

Before removing the original MSI-X interrupt handler, all dup-ed interrupt handlers associated with this MSI-X interrupt must have been disabled and freed. Otherwise, calls to ddi_intr_remove_handler() will fail with DDI_FAILURE.

See the EXAMPLES section for code that illustrates the use of the ddi_intr_dup_handler() function.

Return Values

The ddi_intr_dup_handler() function returns:

DDI_SUCCESS

On success.

Note that the interface should be verified to ensure that the return value is not equal to DDI_SUCCESS. Incomplete checking for failure codes could result in inconsistent behavior among platforms.

DDI_EINVAL

On encountering invalid input parameters. DDI_EINVAL is also returned if a dup is attempted from a dup-ed interrupt or if the hardware device is found not to support MSI-X interrupts.

DDI_FAILURE

On any implementation specific failure.

Examples

Example 1 Using the `ddi_intr_dup_handler()` function

int
add_msix_interrupts(intr_state_t *state)
{
    int x, y;

    /*
     * For this example, assume the device supports multiple
     * interrupt vectors, but only request to be allocated
     * 1 MSI-X to use and then dup the rest.
     */
    if (ddi_intr_get_nintrs(state->dip, DDI_INTR_TYPE_MSIX,
        &state->intr_count) != DDI_SUCCESS) {
            cmn_err(CE_WARN, "Failed to retrieve the MSI-X interrupt count");
            return (DDI_FAILURE);
    }

    state->intr_size = state->intr_count * sizeof (ddi_intr_handle_t);
    state->intr_htable = kmem_zalloc(state->intr_size, KM_SLEEP);

    /* Allocate one MSI-X interrupt handle */
    if (ddi_intr_alloc(state->dip, state->intr_htable,
        DDI_INTR_TYPE_MSIX, state->inum, 1, &state->actual,
        DDI_INTR_ALLOC_STRICT) != DDI_SUCCESS) {
            cmn_err(CE_WARN, "Failed to allocate MSI-X interrupt");
            kmem_free(state->intr_htable, state->intr_size);
            return (DDI_FAILURE);
    }

    /* Get the count of how many MSI-X interrupts we dup */
    state->dup_cnt = state->intr_count - state->actual;

    if (ddi_intr_get_pri(state->intr_htable[0],
        &state->intr_pri) != DDI_SUCCESS) {
            cmn_err(CE_WARN, "Failed to get interrupt priority");
            goto error1;
    }

    /* Make sure the MSI-X priority is below 'high level' */
    if (state->intr_pri >= ddi_intr_get_hilevel_pri()) {
            cmn_err(CE_WARN, "Interrupt PRI is too high");
            goto error1;
    }

    /*
     * Add the handler for the interrupt
     */
    if (ddi_intr_add_handler(state->intr_htable[0],
        (ddi_intr_handler_t *)intr_isr, (caddr_t)state,
        NULL) != DDI_SUCCESS) {
            cmn_err(CE_WARN, "Failed to add interrupt handler");
            goto error1;
    }

    /* Enable the main MSI-X handle first */
    if (ddi_intr_enable(state->intr_htable[0]) != DDI_SUCCESS) {
            cmn_err(CE_WARN, "Failed to enable interrupt");
            goto error2;
    }

    /*
     * Create and enable dups of the original MSI-X handler, note
     * that the inum we are using starts at 0.
     */
    for (x = 1; x < state->dup_cnt; x++) {
        if (ddi_intr_dup_handler(state->intr_htable[0],
            state->inum + x, &state->intr_htable[x]) != DDI_SUCCESS) {
                for (y = x - 1; y > 0; y--) {
                    (void) ddi_intr_disable(state->intr_htable[y]);
                    (void) ddi_intr_free(state->intr_htable[y]);
                }

            goto error2;
        }
        if (ddi_intr_enable(state->intr_htable[x]) != DDI_SUCCESS) {
            for (y = x; y > 0; y--) {
                (void) ddi_intr_disable(state->intr_htable[y]);
                (void) ddi_intr_free(state->intr_htable[y]);
            }
                
            goto error2;
        }
    }

    return (DDI_SUCCESS);

error2:
    (void) ddi_intr_remove_handler(state->intr_htable[0]);
error1:
    (void) ddi_intr_free(state->intr_htable[0]);

    kmem_free(state->intr_htable, state->intr_size);
    return (DDI_FAILURE);
}

void
remove_msix_interrupts(intr_state_t *state)
{
    int x;

    /* 
     * Disable all the handles and free the dup-ed handles
     * before we can remove the main MSI-X interrupt handle.
     */
    for (x = 1; x < state->dup_cnt; x++) {
        (void) ddi_intr_disable(state->intr_htable[x]);
        (void) ddi_intr_free(state->intr_htable[x]);
    }

    /*
     * We can remove and free the main MSI-X handler now
     * that all the dups have been freed.
     */
    (void) ddi_intr_disable(state->intr_htable[0]);
    (void) ddi_intr_remove_handler(state->intr_htable[0]);
    (void) ddi_intr_free(state->intr_htable[0]);

    kmem_free(state->intr_htable, state->intr_size);
}

Context

The ddi_intr_dup_handler() function can be called from kernel non-interrupt context.

Attributes

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

ATTRIBUTE TYPE	ATTRIBUTE VALUE
Interface Stability	Evolving