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_contextmgt)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 5.11							    22 Jan 1997 					      devmap_do_ctxmgt(9F)