Tribblix: manual page: ddi_add

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

NAME

ddi_add_softintr, ddi_get_soft_iblock_cookie, ddi_remove_softintr,
ddi_trigger_softintr - software interrupt handling routines

SYNOPSIS

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

int ddi_get_soft_iblock_cookie(dev_info_t *dip,
int preference, ddi_iblock_cookie_t *iblock_cookiep);

int ddi_add_softintr(dev_info_t *dip, int preference, ddi_softintr_t *idp,
ddi_iblock_cookie_t *iblock_cookiep, ddi_idevice_cookie_t *
idevice_cookiep,
uint_t(*int_handler) (caddr_t int_handler_arg), caddr_t
int_handler_arg);

void ddi_remove_softintr(ddi_softintr_t id);

void ddi_trigger_softintr(ddi_softintr_t id);

INTERFACE LEVEL

illumos DDI specific (illumos DDI). These interfaces are obsolete.
Use the new interrupt interfaces referenced in Intro(9F). Refer to
Writing Device Drivers for more information.

PARAMETERS

ddi_get_soft_iblock_cookie()

dip
Pointer to a dev_info structure.

preference
The type of soft interrupt to retrieve the cookie
for.

iblock_cookiep
Pointer to a location to store the interrupt block
cookie.

ddi_add_softintr()

dip
Pointer to dev_info structure.

preference
A hint value describing the type of soft interrupt
to generate.

idp
Pointer to a soft interrupt identifier where a
returned soft interrupt identifier is stored.

iblock_cookiep
Optional pointer to an interrupt block cookie
where a returned interrupt block cookie is stored.

idevice_cookiep
Optional pointer to an interrupt device cookie
where a returned interrupt device cookie is stored
(not used).

int_handler
Pointer to interrupt handler.

int_handler_arg
Argument for interrupt handler.

ddi_remove_softintr()

id
The identifier specifying which soft interrupt handler to
remove.

ddi_trigger_softintr()

id
The identifier specifying which soft interrupt to trigger and
which soft interrupt handler will be called.

DESCRIPTION

For ddi_get_soft_iblock_cookie():

ddi_get_soft_iblock_cookie() retrieves the interrupt block cookie
associated with a particular soft interrupt preference level. This
routine should be called before ddi_add_softintr() to retrieve the
interrupt block cookie needed to initialize locks (mutex(9F),
rwlock(9F)) used by the software interrupt routine. preference
determines which type of soft interrupt to retrieve the cookie for.
The possible values for preference are:

DDI_SOFTINT_LOW
Low priority soft interrupt.

DDI_SOFTINT_MED
Medium priority soft interrupt.

DDI_SOFTINT_HIGH
High priority soft interrupt.

On a successful return, iblock_cookiep contains information needed
for initializing locks associated with this soft interrupt (see
mutex_init(9F) and rw_init(9F)). The driver can then initialize
mutexes acquired by the interrupt routine before calling
ddi_add_softintr() which prevents a possible race condition where the
driver's soft interrupt handler is called immediately after the
driver has called ddi_add_softintr() but before the driver has
initialized the mutexes. This can happen when a soft interrupt for a
different device occurs on the same soft interrupt priority level. If
the soft interrupt routine acquires the mutex before it has been
initialized, undefined behavior may result.

For ddi_add_softintr():

ddi_add_softintr() adds a soft interrupt to the system. The user
specified hint preference identifies three suggested levels for the
system to attempt to allocate the soft interrupt priority at. The
value for preference should be the same as that used in the
corresponding call to ddi_get_soft_iblock_cookie(). Refer to the
description of ddi_get_soft_iblock_cookie() above.

The value returned in the location pointed at by idp is the soft
interrupt identifier. This value is used in later calls to
ddi_remove_softintr() and ddi_trigger_softintr() to identify the soft
interrupt and the soft interrupt handler.

The value returned in the location pointed at by iblock_cookiep is an
interrupt block cookie which contains information used for
initializing mutexes associated with this soft interrupt (see
mutex_init(9F) and rw_init(9F)). Note that the interrupt block cookie
is normally obtained using ddi_get_soft_iblock_cookie() to avoid the
race conditions described above (refer to the description of
ddi_get_soft_iblock_cookie() above). For this reason, iblock_cookiep
is no longer useful and should be set to NULL.

idevice_cookiep is not used and should be set to NULL.

The routine int_handler, with its argument int_handler_arg, is called
upon receipt of a software interrupt. Software interrupt handlers
must not assume that they have work to do when they run, since (like
hardware interrupt handlers) they may run because a soft interrupt
occurred for some other reason. For example, another driver may have
triggered a soft interrupt at the same level. For this reason, before
triggering the soft interrupt, the driver must indicate to its soft
interrupt handler that it should do work. This is usually done by
setting a flag in the state structure. The routine int_handler checks
this flag, reachable through int_handler_arg, to determine if it
should claim the interrupt and do its work.

The interrupt handler must return DDI_INTR_CLAIMED if the interrupt
was claimed, DDI_INTR_UNCLAIMED otherwise.

If successful, ddi_add_softintr() will return DDI_SUCCESS; if the
interrupt information cannot be found, it will return DDI_FAILURE.

For ddi_remove_softintr():

ddi_remove_softintr() removes a soft interrupt from the system. The
soft interrupt identifier id, which was returned from a call to
ddi_add_softintr(), is used to determine which soft interrupt and
which soft interrupt handler to remove. Drivers must remove any soft
interrupt handlers before allowing the system to unload the driver.

For ddi_trigger_softintr():

ddi_trigger_softintr() triggers a soft interrupt. The soft interrupt
identifier id is used to determine which soft interrupt to trigger.
This function is used by device drivers when they wish to trigger a
soft interrupt which has been set up using ddi_add_softintr().

RETURN VALUES

ddi_add_softintr() and ddi_get_soft_iblock_cookie() return:

DDI_SUCCESS
on success

DDI_FAILURE
on failure

CONTEXT

These functions can be called from user or kernel context.
ddi_trigger_softintr() may be called from high-level interrupt
context as well.

EXAMPLES

Example 1: device using high-level interrupts

In the following example, the device uses high-level interrupts.
High-level interrupts are those that interrupt at the level of the
scheduler and above. High level interrupts must be handled without
using system services that manipulate thread or process states,
because these interrupts are not blocked by the scheduler. In
addition, high level interrupt handlers must take care to do a
minimum of work because they are not preemptable. See
ddi_intr_hilevel(9F).

In the example, the high-level interrupt routine minimally services
the device, and enqueues the data for later processing by the soft
interrupt handler. If the soft interrupt handler is not currently
running, the high-level interrupt routine triggers a soft interrupt
so the soft interrupt handler can process the data. Once running, the
soft interrupt handler processes all the enqueued data before
returning.

The state structure contains two mutexes. The high-level mutex is
used to protect data shared between the high-level interrupt handler
and the soft interrupt handler. The low-level mutex is used to
protect the rest of the driver from the soft interrupt handler.

struct xxstate {
...
ddi_softintr_t id;
ddi_iblock_cookie_t high_iblock_cookie;
kmutex_t high_mutex;
ddi_iblock_cookie_t low_iblock_cookie;
kmutex_t low_mutex;
int softint_running;
...
};
struct xxstate *xsp;
static uint_t xxsoftintr(caddr_t);
static uint_t xxhighintr(caddr_t);
...

Example 2: sample attach() routine

The following code fragment would usually appear in the driver's
attach(9E) routine. ddi_add_intr(9F) is used to add the high-level
interrupt handler and ddi_add_softintr() is used to add the low-level
interrupt routine.

static uint_t
xxattach(dev_info_t *dip, ddi_attach_cmd_t cmd)
{
struct xxstate *xsp;
...
/* get high-level iblock cookie */
if (ddi_get_iblock_cookie(dip, inumber,
&xsp->high_iblock_cookie) != DDI_SUCCESS) {
/* clean up */
return (DDI_FAILURE); /* fail attach */
}

/* initialize high-level mutex */
mutex_init(&xsp->high_mutex, "xx high mutex", MUTEX_DRIVER,
(void *)xsp->high_iblock_cookie);

/* add high-level routine - xxhighintr() */
if (ddi_add_intr(dip, inumber, NULL, NULL,
xxhighintr, (caddr_t) xsp) != DDI_SUCCESS) {
/* cleanup */
return (DDI_FAILURE); /* fail attach */
}

/* get soft iblock cookie */
if (ddi_get_soft_iblock_cookie(dip, DDI_SOFTINT_MED,
&xsp->low_iblock_cookie) != DDI_SUCCESS) {
/* clean up */
return (DDI_FAILURE); /* fail attach */
}

/* initialize low-level mutex */
mutex_init(&xsp->low_mutex, "xx low mutex", MUTEX_DRIVER,
(void *)xsp->low_iblock_cookie);

/* add low level routine - xxsoftintr() */
if ( ddi_add_softintr(dip, DDI_SOFTINT_MED, &xsp->id,
NULL, NULL, xxsoftintr, (caddr_t) xsp) != DDI_SUCCESS) {
/* cleanup */
return (DDI_FAILURE); /* fail attach */
}

...
}

Example 3: High-level interrupt routine

The next code fragment represents the high-level interrupt routine.
The high-level interrupt routine minimally services the device, and
enqueues the data for later processing by the soft interrupt routine.
If the soft interrupt routine is not already running,
ddi_trigger_softintr() is called to start the routine. The soft
interrupt routine will run until there is no more data on the queue.

static uint_t
xxhighintr(caddr_t arg)
{
struct xxstate *xsp = (struct xxstate *) arg;
int need_softint;
...
mutex_enter(&xsp->high_mutex);
/*
* Verify this device generated the interrupt
* and disable the device interrupt.
* Enqueue data for xxsoftintr() processing.
*/

/* is xxsoftintr() already running ? */
if (xsp->softint_running)
need_softint = 0;
else
need_softint = 1;
mutex_exit(&xsp->high_mutex);

/* read-only access to xsp->id, no mutex needed */
if (need_softint)
ddi_trigger_softintr(xsp->id);
...
return (DDI_INTR_CLAIMED);
}

static uint_t
xxsoftintr(caddr_t arg)
{
struct xxstate *xsp = (struct xxstate *) arg;
...
mutex_enter(&xsp->low_mutex);
mutex_enter(&xsp->high_mutex);

/* verify there is work to do */
if (work queue empty || xsp->softint_running ) {
mutex_exit(&xsp->high_mutex);
mutex_exit(&xsp->low_mutex);
return (DDI_INTR_UNCLAIMED);
}

xsp->softint_running = 1;

while ( data on queue ) {
ASSERT(mutex_owned(&xsp->high_mutex));

/* de-queue data */

mutex_exit(&xsp->high_mutex);

/* Process data on queue */

mutex_enter(&xsp->high_mutex);
}

xsp->softint_running = 0;
mutex_exit(&xsp->high_mutex);
mutex_exit(&xsp->low_mutex);

return (DDI_INTR_CLAIMED);
}

ATTRIBUTES

NOTES

ddi_add_softintr() may not be used to add the same software interrupt
handler more than once. This is true even if a different value is
used for int_handler_arg in each of the calls to ddi_add_softintr().
Instead, the argument passed to the interrupt handler should indicate
what service(s) the interrupt handler should perform. For example,
the argument could be a pointer to the device's soft state structure,
which could contain a 'which_service' field that the handler
examines. The driver must set this field to the appropriate value
before calling ddi_trigger_softintr().

February 17, 2023 DDI_ADD_SOFTINTR(9F)