Tribblix: manual page: ddi_check_acc

DDI_CHECK_ACC_HANDLE(9F) Kernel Functions for Drivers

NAME

ddi_check_acc_handle, ddi_check_dma_handle - Check data access and
DMA handles

SYNOPSIS

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

int ddi_check_acc_handle(ddi_acc_handle_t acc_handle );

int ddi_check_dma_handle(ddi_dma_handle_t dma_handle );

INTERFACE LEVEL

illumos DDI specific (illumos DDI)

PARAMETERS

acc_handle
Data access handle obtained from a previous call to
ddi_regs_map_setup(9F), ddi_dma_mem_alloc(9F), or
similar function.

dma_handle
DMA handle obtained from ddi_dma_alloc_handle(9F).

DESCRIPTION

The ddi_check_acc_handle() and ddi_check_dma_handle() 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.

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, ddi_get8(9F)) may
return random values, and write accesses (for example, ddi_put8(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
ddi_dev_report_fault(9F) specifying DDI_SERVICE_LOST for the impact,
and DDI_DATAPATH_FAULT for the location.

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.

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 does exist with respect to
communication using that handle.

RETURN VALUES

The ddi_check_acc_handle() and ddi_check_dma_handle() functions
return DDI_SUCCESS if no faults affecting the supplied handle are
detected and DDI_FAILURE if any fault affecting the supplied handle
is detected.

EXAMPLES

static int
xxattach(dev_info_t *dip, ddi_attach_cmd_t cmd)
{
...
/* This driver uses only a single register-access handle */
status = ddi_regs_map_setup(dip, REGSET_ZERO, ®addr,
0, 0, , &acc_attrs, &acc_hdl);
if (status != DDI_SUCCESS)
return (DDI_FAILURE);
...
}

static int
xxread(dev_t dev, struct uio *uio_p, cred_t *cred_p)
{
...
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);
}
...

CONTEXT

The ddi_check_acc_handle() and ddi_check_dma_handle() functions may
be called from user, kernel, or interrupt context.