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ddi_add_softintr(9f)
ddi_add_softintr(9F) Kernel Functions 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
Solaris DDI specific (Solaris DDI). These interfaces are obsolete. Use
the new interrupt interfaces referenced in Intro(9F). Refer to Writing
Device Drivers in Oracle Solaris 11.4 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 re‐
turned 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 asso‐
ciated 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 mu‐
tex_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 inter‐
rupt 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 speci‐
fied 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 inter‐
rupt identifier. This value is used in later calls to ddi_remove_soft‐
intr() 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 de‐
scribed 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 hard‐
ware 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 han‐
dler that it should do work. This is usually done by setting a flag in
the state structure. The routine int_handler checks this flag, reach‐
able through int_handler_arg, to determine if it should claim the in‐
terrupt 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 in‐
terrupt 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 inter‐
rupt 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_trig‐
ger_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 inter‐
rupts are not blocked by the scheduler. In addition, high level inter‐
rupt 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 inter‐
rupt 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 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 at‐
tach(9E) routine. ddi_add_intr(9F) is used to add the high-level inter‐
rupt handler and ddi_add_softintr() is used to add the low-level inter‐
rupt 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) {
/* clean up */
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) {
/* clean up */
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 en‐
queues the data for later processing by the soft interrupt routine. If
the soft interrupt routine is not already running, ddi_trigger_soft‐
intr() 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
See attributes(7) for descriptions of the following attributes:
tab() box; cw(2.75i) |cw(2.75i) lw(2.75i) |lw(2.75i) ATTRIBUTE TYPEAT‐
TRIBUTE VALUE _ Interface StabilityObsolete
SEE ALSO
Intro(9F), ddi_add_intr(9F), ddi_in_panic(9F), ddi_intr_hilevel(9F),
ddi_remove_intr(9F), mutex_init(9F)
Writing Device Drivers in Oracle Solaris 11.4
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(). In‐
stead, 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().
Oracle Solaris 11.4 11 May 2021 ddi_add_softintr(9F)