devmap_contextmgt man page on Solaris

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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_con‐
       textmgt()   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_con‐
       textmgt()   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	 allo‐
       cated  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

SunOS 5.10			  16 Jan 1997		 devmap_contextmgt(9E)
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