devmap_access man page on SunOS

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devmap_access(9E)	      Driver Entry Points	     devmap_access(9E)

NAME
       devmap_access - device mapping access entry point

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

       int  prefixdevmap_access(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.

		DEVMAP_EXEC	Execution access attempted.

DESCRIPTION
       The devmap_access() entry point is an optional  routine.	  It  notifies
       drivers	whenever an access is made to a mapping described by  dhp that
       has not been validated or does  not have sufficient protection for  the
       access.	  The	system	 expects   devmap_access()   to	  call	either
       devmap_do_ctxmgt(9F) or devmap_default_access(9F) to  load  the	memory
       address	translations before it returns. For mappings that support con‐
       text switching,	device drivers should call  devmap_do_ctxmgt(9F).  For
       mappings that do not support context switching, the drivers should call
       devmap_default_access(9F).

       In  devmap_access(), drivers perform memory access  related  operations
       such  as	 context  switching,  checking	the availability of the memory
       object, and locking and unlocking the memory object being accessed. The
       devmap_access() entry point is set to  NULL if no operations need to be
       performed.

       pvtp is a pointer to the driver's private mapping data that  was	 allo‐
       cated and initialized in the devmap_map(9E) entry point.

       off  and	 len  define  the  range  to  be affected by the operations in
       devmap_access(). 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_do_ctxmgt(9F)  or
       devmap_default_access(9F) must be same as  len. rw specifies the direc‐
       tion of access on the memory object.

       A non-zero return value from  devmap_access() may result in  a  SIGSEGV
       or SIGBUS signal being delivered to the process.

RETURN VALUES
       devmap_access() returns the following values:

       0	       Successful completion.

       Non-zero	       An    error    occurred.	   The	 return	  value	  from
		       devmap_do_ctxmgt(9F)    or    devmap_default_access(9F)
		       should be returned.

EXAMPLES
       Example 1: devmap_access() entry point

       The following is an example of the devmap_access() entry point.	If the
       mapping	 supports    context	switching,    devmap_access()	 calls
       devmap_do_ctxmgt(9F).	   Otherwise,	    devmap_access()	 calls
       devmap_default_access(9F).

       ...
       #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_map(9E),	  devmap_default_access(9F),	 devmap_do_ctxmgt(9F),
       devmap_callback_ctl(9S)

       Writing Device Drivers

SunOS 5.10			  17 Jan 1997		     devmap_access(9E)
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