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

#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);

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

ddi_get_soft_iblock_cookie()

dip

preference

iblock_cookiep

ddi_add_softintr()

dip

preference

idp

iblock_cookiep

idevice_cookiep

int_handler

int_handler_arg

ddi_remove_softintr()

id

ddi_trigger_softintr()

id

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

DDI_SOFTINT_MED

DDI_SOFTINT_HIGH

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().

ddi_add_softintr() and ddi_get_soft_iblock_cookie() return:

DDI_SUCCESS

DDI_FAILURE

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

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);
}

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

ATTRIBUTE TYPE	ATTRIBUTE VALUE
Interface Stability	Obsolete

ddi_add_intr(9F), ddi_in_panic(9F), ddi_intr_hilevel(9F), ddi_remove_intr(9F), Intro(9F), mutex_init(9F)

Writing Device Drivers

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().