ddi_get_soft_iblock_cookie(9F)
NAME
ddi_add_softintr, ddi_get_soft_iblock_cookie,
ddi_remove_softintr, ddi_trigger_softintr - software inter-
rupt 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 prefer-
ence, 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
Solaris DDI specific (Solaris DDI).
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 prefer-
ence 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 pos-
sible 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 rou-
tine before calling ddi_add_softintr() which prevents a pos-
sible 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 dif-
ferent 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 inter-
rupt 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 iden-
tify 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 condi-
tions 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 inter-
rupt 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 sys-
tem. 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 inter-
rupt context as well.
EXAMPLES
Example 1: device using high-level interrupts
In the following example, the device uses high-level inter-
rupts. 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 pro-
cessing 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 inter-
rupt handler processes all the enqueued data before return-
ing.
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);
}
SEE ALSO
ddi_add_intr(9F), ddi_in_panic(9F), ddi_intr_hilevel(9F),
ddi_remove_intr(9F), mutex_init(9F)
Writing Device Drivers
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().
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