devmap_unload man page on SmartOS

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DEVMAP_UNLOAD(9F)					     DEVMAP_UNLOAD(9F)

NAME
       devmap_unload,  devmap_load  -  control	validation  of	memory address
       translations

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

       int devmap_load(devmap_cookie_t dhp, offset_t off, size_t len,
	    uint_t type, uint_t rw);

       int devmap_unload(devmap_cookie_t dhp, offset_t off, size_t len);

INTERFACE LEVEL
       Solaris DDI specific (Solaris DDI).

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

       off
	       User offset within the logical device memory at which the load‐
	       ing or unloading of the address translations begins.

       len
	       Length (in bytes) of the range being affected.

   devmap_load() only
       type
		Type of access operation.

       rw
		Direction of access.

DESCRIPTION
       devmap_unload() and devmap_load() are used to control the validation of
       the   memory   mapping	described  by  dhp  in	the  specified	range.
       devmap_unload() invalidates the mapping translations and will  generate
       calls  to  the  devmap_access(9E)  entry point next time the mapping is
       accessed. The drivers use devmap_load() to validate the mapping	trans‐
       lations during memory access.

       A  typical  use of devmap_unload() and devmap_load() is in the driver's
       context management callback function, devmap_contextmgt(9E). To	manage
       a  device context, a device driver calls devmap_unload() on the context
       about to	 be  switched  out.  It	 switches  contexts,  and  then	 calls
       devmap_load() on the context switched in.   devmap_unload() can be used
       to unload the mappings of other processes as well as  the  mappings  of
       the  calling  process,  but  devmap_load() can only be used to load the
       mappings of the calling process. Attempting to load  another  process's
       mappings with devmap_load() will result in a system panic.

       For  both  routines, the range to be affected is defined by the off and
       len arguments. Requests affect the entire page containing the  off  and
       all  pages  up  to  and	including the page containing the last byte as
       indicated by off + len. The arguments type and rw are provided  by  the
       system to the calling function (for example, devmap_contextmgt(9E)) and
       should not be modified.

       Supplying a value of  0 for the len argument affects all addresses from
       the  off to the end of the mapping.  Supplying a value of 0 for the off
       argument and a value of 0 for len argument affect all addresses in  the
       mapping.

       A  non-zero  return  value from either devmap_unload() or devmap_load()
       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.

CONTEXT
       These routines can be called from user or kernel context only.

EXAMPLES
       Example 1 Managing a One-Page Device Context

       The following shows an example of managing a device context that is one
       page in length.

	 struct xx_context cur_ctx;

	 static int
	 xxdevmap_contextmgt(devmap_cookie_t dhp, void *pvtp, offset_t off,
	    size_t len, uint_t type, uint_t rw)
	 {
	     int err;
	     devmap_cookie_t cur_dhp;
	     struct xx_pvt *p;
	     struct xx_pvt *pvp = (struct xx_pvt *)pvtp;
	     /* enable access callbacks for the current mapping */
	     if (cur_ctx != NULL && cur_ctx != pvp->ctx) {
		 p = cur_ctx->pvt;
		 /*
		  * unload the region from off to the end of the mapping.
		  */
		 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;
	     /*
	      * Disable callbacks and complete the access for the
	      * mapping that generated this callback.
	      */
	     return (devmap_load(pvp->dhp, off, len, type, rw));
	 }

SEE ALSO
       devmap_access(9E), devmap_contextmgt(9E)

       Writing Device Drivers

				 Jan 22, 1997		     DEVMAP_UNLOAD(9F)
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