'\" te
.\"  Copyright (c) 1999, Sun Microsystems, Inc.  All Rights Reserved
.TH ddi_check_acc_handle 9F "13 August 1999" "SunOS 5.11" "Kernel Functions for Drivers"
.SH NAME
ddi_check_acc_handle, ddi_check_dma_handle \- Check data access and DMA handles
.SH SYNOPSIS
.LP
.nf
#include <sys/ddi.h> 
#include <sys/sunddi.h>

\fBint\fR \fBddi_check_acc_handle\fR(\fBddi_acc_handle_t\fR \fI acc_handle\fR );
.fi

.LP
.nf
\fBint\fR \fBddi_check_dma_handle\fR(\fBddi_dma_handle_t\fR  \fIdma_handle\fR );
.fi

.SH INTERFACE LEVEL
.sp
.LP
Solaris DDI specific (Solaris DDI)
.SH PARAMETERS
.sp
.ne 2
.mk
.na
\fB\fIacc_handle\fR \fR
.ad
.RS 15n
.rt  
Data access handle obtained from a previous call to \fBddi_regs_map_setup\fR(9F), \fBddi_dma_mem_alloc\fR(9F), or similar function.
.RE

.sp
.ne 2
.mk
.na
\fB\fIdma_handle\fR \fR
.ad
.RS 15n
.rt  
DMA handle obtained from a previous call to \fBddi_dma_setup\fR(9F) or one of its derivatives. 
.RE

.SH DESCRIPTION
.sp
.LP
The \fBddi_check_acc_handle()\fR\fB and ddi_check_dma_handle()\fR functions check for faults that can interfere with communication between a driver and the device it controls. Each function checks a single handle of a specific type and returns a status value indicating whether faults affecting the resource mapped by the supplied handle have been detected. 
.sp
.LP
If a fault is indicated when checking a data access handle, this implies that the driver is no longer able to access the mapped registers or memory using programmed I/O through that handle.  Typically, this might occur after the device has failed to respond to an I/O access (for example, has incurred a bus error or timed out). The effect of programmed I/O accesses made after this happens is undefined; for example, read accesses (for example, \fBddi_get8\fR(9F)) may return random values, and write accesses (for example, \fBddi_put8\fR(9F)) may or may not have any effect. This type of fault is normally fatal to the operation of the device, and the driver should report it via \fBddi_dev_report_fault\fR(9F) specifying \fBDDI_SERVICE_LOST\fR for the impact, and \fBDDI_DATAPATH_FAULT\fR for the location.
.sp
.LP
If a fault is indicated when checking a DMA handle, it implies that a fault has been detected that has (or will) affect DMA transactions between the device and the memory currently bound to the handle (or most recently bound, if the handle is currently unbound). Possible causes include the failure of a component in the DMA data path, or an attempt by the device to make an invalid DMA access. The driver may be able to continue by falling back to a non-DMA mode of operation, but in general, DMA faults are non-recoverable.  The contents of the memory currently (or previously) bound to the handle should be regarded as indeterminate. The fault indication associated with the current transaction is lost once the handle is (re-)bound, but because the fault may persist, future DMA operations may not succeed.
.sp
.LP
Note that some implementations cannot detect all types of failure. If a fault is not indicated, this does not constitute a guarantee that communication is possible. However, if a check fails, this is a positive indication that a problem \fBdoes\fR exist with respect to communication using that handle.
.SH RETURN VALUES
.sp
.LP
The \fBddi_check_acc_handle()\fR and \fBddi_check_dma_handle()\fR functions return \fBDDI_SUCCESS\fR if no faults affecting the supplied handle are detected and \fBDDI_FAILURE\fR if any fault affecting the supplied handle is detected.
.SH EXAMPLES
.sp
.in +2
.nf
static int
xxattach(dev_info_t *dip, ddi_attach_cmd_t cmd)
{
    \e&...
    /* This driver uses only a single register-access handle */
    status = ddi_regs_map_setup(dip, REGSET_ZERO, &regaddr,
                                0, 0, , &acc_attrs, &acc_hdl);
    if (status != DDI_SUCCESS)
        return (DDI_FAILURE);
    \e&...
}

static int
xxread(dev_t  dev, struct uio *uio_p, cred_t *cred_p)
{
    \e&...
    if (ddi_check_acc_handle(acc_hdl) != DDI_SUCCESS) {
        ddi_dev_report_fault(dip, DDI_SERVICE_LOST,
            DDI_DATAPATH_FAULT, "register access fault during read");
        return (EIO);
    }
    \e&...
.fi
.in -2

.SH CONTEXT
.sp
.LP
The \fBddi_check_acc_handle()\fR and \fBddi_check_dma_handle()\fR functions may be called from user, kernel, or interrupt context.
.SH SEE ALSO
.sp
.LP
\fBddi_regs_map_setup\fR(9F), \fBddi_dma_setup\fR(9F), \fBddi_dev_report_fault\fR(9F), \fBddi_get8\fR(9F), \fBddi_put8\fR(9F)