DEVMAP_CONTEXTMGT(9E) Driver Entry Points DEVMAP_CONTEXTMGT(9E)


NAME


devmap_contextmgt - driver callback function for context management

SYNOPSIS


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


int devmap_contextmgt(devmap_cookie_t dhp, void *pvtp,
offset_t off, size_t len, uint_t type, uint_t rw);


INTERFACE LEVEL


Solaris DDI specific (Solaris DDI).

ARGUMENTS


dhp
An opaque mapping handle that the system uses to describe the
mapping.


pvtp
Driver private mapping data.


off
User offset within the logical device memory at which the access
begins.


len
Length (in bytes) of the memory being accessed.


type
Type of access operation. Possible values are:

DEVMAP_ACCESS
Memory access.


DEVMAP_LOCK
Lock the memory being accessed.


DEVMAP_UNLOCK
Unlock the memory being accessed.


rw
Direction of access. Possible values are:

DEVMAP_READ
Read access attempted.


DEVMAP_WRITE
Write access attempted.


DESCRIPTION


devmap_contextmgt() is a driver-supplied function that performs device
context switching on a mapping. Device drivers pass devmap_contextmgt()
as an argument to devmap_do_ctxmgt(9F) in the devmap_access(9E) entry
point. The system will call devmap_contextmgt() when memory is accessed.
The system expects devmap_contextmgt() to load the memory address
translations of the mapping by calling devmap_load(9F) before returning.


dhp uniquely identifies the mapping and is used as an argument to
devmap_load(9F) to validate the mapping. off and len define the range to
be affected by the operations in devmap_contextmgt().


The driver must check if there is already a mapping established at off
that needs to be unloaded. If a mapping exists at off,
devmap_contextmgt() must call devmap_unload(9F) on the current mapping.
devmap_unload(9F) must be followed by devmap_load() on the mapping that
generated this call to devmap_contextmgt(). devmap_unload(9F) unloads
the current mapping so that a call to devmap_access(9E), which causes the
system to call devmap_contextmgt(), will be generated the next time the
mapping is accessed.


pvtp is a pointer to the driver's private mapping data that was allocated
and initialized in the devmap_map(9E) entry point. type defines the type
of operation that device drivers should perform on the memory object. If
type is either DEVMAP_LOCK or DEVMAP_UNLOCK, the length passed to either
devmap_unload(9F) or devmap_load(9F) must be same as len. rw specifies
the access direction on the memory object.


A non-zero return value from devmap_contextmgt() will be returned to
devmap_access(9E) and will cause the corresponding operation to fail. The
failure may result in a SIGSEGV or SIGBUS signal being delivered to the
process.

RETURN VALUES


0
Successful completion.


Non-zero
An error occurred.


EXAMPLES


Example 1: managing a device context




The following shows an example of managing a device context.


struct xxcontext cur_ctx;
static int
xxdevmap_contextmgt(devmap_cookie_t dhp, void *pvtp, offset_t off,
size_t len, uint_t type, uint_t rw)
{
devmap_cookie_t cur_dhp;
struct xxpvtdata *p;
struct xxpvtdata *pvp = (struct xxpvtdata *)pvtp;
struct xx_softc *softc = pvp->softc;
int err;

mutex_enter(&softc->mutex);

/*
* invalidate the translations of current context before
* switching context.
*/
if (cur_ctx != NULL && cur_ctx != pvp->ctx) {
p = cur_ctx->pvt;
cur_dhp = p->dhp;
if ((err = devmap_unload(cur_dhp, off, len)) != 0)
return (err);
}
/* Switch device context - device dependent*/
...
/* Make handle the new current mapping */
cur_ctx = pvp->ctx;

/*
* Load the address translations of the calling context.
*/
err = devmap_load(pvp->dhp, off, len, type, rw);

mutex_exit(&softc->mutex);

return (err);
}


SEE ALSO


devmap_access(9E), devmap_do_ctxmgt(9F) devmap_load(9F),
devmap_unload(9F)


Writing Device Drivers


January 16, 1997 DEVMAP_CONTEXTMGT(9E)