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.\" Copyright (c) 1997, Oracle and/or its affiliates. All rights reserved.
.TH devmap_access 9E "17 Jan 1997" "Oracle Solaris 11.4" "Driver Entry Points"
.SH NAME
devmap_access \- device mapping access entry point
.SH SYNOPSIS

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

\fBint prefix\fR\fBdevmap_access\fR(\fBdevmap_cookie_t\fR \fIdhp\fR, \fBvoid *\fR\fIpvtp\fR, 
     \fBoffset_t\fR \fIoff\fR, \fBsize_t\fR \fIlen\fR, \fBuint_t\fR \fItype\fR, \fBuint_t\fR \fIrw\fR);
.fi
.SH INTERFACE LEVEL
.sp
.LP
Solaris DDI specific (Solaris DDI).
.SH ARGUMENTS
.sp
.ne 2
.mk
.na
\fB\fIdhp\fR \fR
.ad
.RS 8n
.rt
An opaque mapping handle that the system uses to describe the mapping.
.RE

.sp
.ne 2
.mk
.na
\fB\fIpvtp\fR \fR
.ad
.RS 8n
.rt
Driver private mapping data.
.RE

.sp
.ne 2
.mk
.na
\fB\fIoff\fR \fR
.ad
.RS 8n
.rt
User offset within the logical device memory at which the access begins.
.RE

.sp
.ne 2
.mk
.na
\fB\fIlen\fR \fR
.ad
.RS 8n
.rt
Length (in bytes) of the memory being accessed.
.RE

.sp
.ne 2
.mk
.na
\fB\fItype\fR \fR
.ad
.RS 8n
.rt
Type of access operation. Possible values are: 
.sp
.ne 2
.mk
.na
\fB\fBDEVMAP_ACCESS\fR \fR
.ad
.RS 17n
.rt
Memory access.
.RE

.sp
.ne 2
.mk
.na
\fB\fBDEVMAP_LOCK\fR \fR
.ad
.RS 17n
.rt
Lock the memory being accessed.
.RE

.sp
.ne 2
.mk
.na
\fB\fBDEVMAP_UNLOCK\fR \fR
.ad
.RS 17n
.rt
Unlock the memory being accessed.
.RE

.RE

.sp
.ne 2
.mk
.na
\fB\fIrw\fR \fR
.ad
.RS 8n
.rt
Direction of access. Possible values are: 
.sp
.ne 2
.mk
.na
\fB\fBDEVMAP_READ\fR \fR
.ad
.RS 16n
.rt
Read access attempted.
.RE

.sp
.ne 2
.mk
.na
\fB\fBDEVMAP_WRITE\fR \fR
.ad
.RS 16n
.rt
Write access attempted.
.RE

.sp
.ne 2
.mk
.na
\fB\fBDEVMAP_EXEC\fR \fR
.ad
.RS 16n
.rt
Execution access attempted.
.RE

.RE

.SH DESCRIPTION
.sp
.LP
The \fBdevmap_access()\fR entry point is an optional routine. It notifies drivers whenever an access is made to a mapping described by \fIdhp\fR that has not been validated or does not have sufficient protection for the access. The system expects \fBdevmap_access()\fR to call either \fBdevmap_do_ctxmgt\fR(9F) or \fBdevmap_default_access\fR(9F) to load the memory address translations before it returns. For mappings that support context switching, device drivers should call \fBdevmap_do_ctxmgt\fR(9F). For mappings that do not support context switching, the drivers should call \fBdevmap_default_access\fR(9F). 
.sp
.LP
In \fBdevmap_access()\fR, 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 \fBdevmap_access()\fR entry point is set to \fINULL\fR if no operations need to be performed.
.sp
.LP
\fIpvtp\fR is a pointer to the driver's private mapping data that was allocated and initialized in the \fBdevmap_map\fR(9E) entry point.
.sp
.LP
\fIoff\fR and \fIlen\fR define the range to be affected by the operations in \fBdevmap_access()\fR. \fItype\fR defines the type of operation that device drivers should perform on the memory object. If \fBtype\fR is either \fBDEVMAP_LOCK\fR or \fBDEVMAP_UNLOCK,\fR the length passed to either \fBdevmap_do_ctxmgt\fR(9F) or \fBdevmap_default_access\fR(9F) must be same as \fIlen\fR. \fIrw\fR specifies the direction of access on the memory object.
.sp
.LP
A non-zero return value from \fBdevmap_access()\fR may result in a \fBSIGSEGV\fR or \fBSIGBUS\fR signal being delivered to the process.
.SH RETURN VALUES
.sp
.LP
\fBdevmap_access()\fR returns the following values:
.sp
.ne 2
.mk
.na
\fB\fB0\fR \fR
.ad
.RS 12n
.rt
Successful completion.
.RE

.sp
.ne 2
.mk
.na
\fBNon-zero\fR
.ad
.RS 12n
.rt
An error occurred. The return value from \fBdevmap_do_ctxmgt\fR(9F) or \fBdevmap_default_access\fR(9F) should be returned.
.RE

.SH EXAMPLES
.LP
\fBExample 1\fR 
\fBdevmap_access()\fR entry point

.sp
.LP
The following is an example of the \fBdevmap_access()\fR entry point. If the mapping supports context switching, \fBdevmap_access()\fR calls \fBdevmap_do_ctxmgt\fR(9F). Otherwise, \fBdevmap_access()\fR calls \fBdevmap_default_access\fR(9F).

.sp
.in +2
.nf
\&.\|.\|.
#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 \fIoff\fR 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 \fI off \fRis 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);
}
.fi
.in -2
.sp

.SH SEE ALSO
.sp
.LP
\fBdevmap_map\fR(9E), \fBdevmap_default_access\fR(9F), \fBdevmap_do_ctxmgt\fR(9F), \fBdevmap_callback_ctl\fR(9S)  
.sp
.LP
\fIWriting Device Drivers in Oracle Solaris 11.4\fR