devmap_do_ctxmgt(9F)					   Kernel Functions for Drivers 				      devmap_do_ctxmgt(9F)

NAME

       devmap_do_ctxmgt - perform device context switching on a mapping

SYNOPSIS

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

       int   devmap_do_ctxmgt(devmap_cookie_t	dhp,   void   *pvtp,  offset_t	off,  size_t  len,  uint_t  type,  uint_t  rw,	int  (*devmap_con-
       textmgt)(devmap_cookie_t, void *, offset_t, size_t, uint_t, uint_t));

INTERFACE LEVEL

       Solaris DDI specific (Solaris DDI).

PARAMETERS

       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.

       devmap_contextmgt       The address of driver function that the system will call to perform context switching on a mapping. See devmap_con-
			       textmgt(9E) for details.

       type		       Type of access operation.  Provided by devmap_access(9E).  Should not be modified.

       rw		       Direction of access.  Provided by devmap_access(9E).  Should not be modified.

DESCRIPTION

       Device  drivers	call  devmap_do_ctxmgt()  in  the  devmap_access(9E)  entry  point  to	perform  device  context  switching  on a mapping.
       devmap_do_ctxmgt() passes a pointer to a driver supplied callback function, devmap_contextmgt(9E), to the  system  that	will  perform  the
       actual  device context switching.  If devmap_contextmgt(9E) is not a valid driver callback function, the system will fail the memory access
       operation which will result in a SIGSEGV or SIGBUS signal being delivered to the process.

       devmap_do_ctxmgt() performs context switching on the mapping object identified by dhp and pvtp in the range specified by off and  len.  The
       arguments dhp, pvtp, type, and rw are provided by the devmap_access(9E) entry point and must not be modified. The range from off to off+len
       must support context switching.

       The system will pass through dhp, pvtp, off,  len, type, and rw to devmap_contextmgt(9E) in order to  perform  the  actual  device  context
       switching.  The return value from devmap_contextmgt(9E) will be returned directly to devmap_do_ctxmgt().

RETURN VALUES

       0	       Successful completion.

       Non-zero        An error occurred.

CONTEXT

       devmap_do_ctxmgt() must be called from the driver's devmap_access(9E) entry point.

EXAMPLES

       Example 1: Using devmap_do_ctxmgt in the devmap_access entry point.

       The following shows an example of using devmap_do_ctxmgt() in the devmap_access(9E) entry point.

       ...
       #define OFF_DO_CTXMGT  0x40000000
       #define OFF_NORMAL     0x40100000
       #define CTXMGT_SIZE    0x100000
       #define NORMAL_SIZE    0x100000

       /*
	* Driver devmap_contextmgt(9E) callback function.
	*/
       static int
       xx_context_mgt(devmap_cookie_t dhp, void *pvtp, offset_t offset,
	   size_t length, uint_t type, uint_t rw)
       {
	   ......
	   /*
	    * see devmap_contextmgt(9E) for an example
	    */
       }

       /*
	* Driver devmap_access(9E) entry point
	*/
       static int
       xxdevmap_access(devmap_cookie_t dhp, void *pvtp, offset_t off,
	   size_t len, uint_t type, uint_t rw)
       {
	   offset_t diff;
	   int err;

	   /*
	    * check if off is within the range that supports
	    * context management.
	    */
	   if ((diff = off - OFF_DO_CTXMG) >= 0 && diff < CTXMGT_SIZE) {
	       /*
		* calculates the length for context switching
		*/
	       if ((len + off) > (OFF_DO_CTXMGT + CTXMGT_SIZE))
		   return (-1);
	       /*
		* perform context switching
		*/
	       err = devmap_do_ctxmgt(dhp, pvtp, off, len, type,
			   rw, xx_context_mgt);
	   /*
	    * check if off is within the range that does normal
	    * memory mapping.
	    */
	   } else if ((diff = off - OFF_NORMAL) >= 0 && diff < NORMAL_SIZE) {
	       if ((len + off) > (OFF_NORMAL + NORMAL_SIZE))
		   return (-1);
	       err = devmap_default_access(dhp, pvtp, off, len, type, rw);
	   } else
	       return (-1);

	   return (err);
       }

SEE ALSO

       devmap_access(9E), devmap_contextmgt(9E), devmap_default_access(9F)

       Writing Device Drivers

SunOS 5.10							    22 Jan 1997 					      devmap_do_ctxmgt(9F)