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The SBus is a geographically addressed
peripheral bus present on many SPARC hardware
platforms. SBus devices are self-identifying -- that is to say the SBus card itself provides information to the system so that it
can identify the device driver that needs to be used. The device usually
provides additional information to the system in the form of name-value
pairs that can be retrieved using the DDI
property interfaces. See ddi_prop_op(9F)
for details.
The information is usually derived from a small Forth program stored
in the FCode PROM on the card, so driver configuration files should be completely
unnecessary for these devices. However, on some occasions, drivers for SBus devices may need to use driver configuration
files to augment the information provided by the SBus card. See driver.conf(4)
for further details.
When they are needed, configuration files for SBus device drivers should identify the parent bus driver implicitly
using the class keyword. This removes the dependency
on the particular bus driver involved since this may be named differently
on different platforms.
All bus drivers of class sbus recognise the following
properties:
-
reg
- An arbitrary length array where each
element of the array consists of a 3-tuple of integers. Each array element
describes a logically contiguous mappable resource on the SBus.
The first integer of each tuple specifies the slot number the card
is plugged into. The second integer of each 3-tuple specifies the offset
in the slot address space identified by the first element. The third integer
of each 3-tuple specifies the size in bytes of the mappable resource.
The driver can refer to the elements of this array by index, and construct
kernel mappings to these addresses using ddi_map_regs(9F). The index into the array
is passed as the rnumber argument of ddi_map_regs().
You can use the ddi_get* and ddi_put* family of functions to access register space from a high-level
interrupt context.
-
interrupts
- An arbitrary length array where each element of the array consists
of a single integer. Each array element describes a possible SBus interrupt level that the device might generate.
The driver can refer to the elements of this array by index, and register
interrupt handlers with the system using ddi_add_intr(9F). The index into the array
is passed as the inumber argument of ddi_add_intr().
-
registers
- An arbitrary length array where each element of the array consists
of a 3-tuple of integers. Each array element describes a logically contiguous
mappable resource on the SBus.
The first integer of each tuple should be set to -1, specifying that any SBus slot may be matched. The second integer
of each 3-tuple specifies the offset in the slot address space identified
by the first element. The third integer of each 3-tuple specifies the size
in bytes of the mappable resoure.
The registers property can only be used to augment
an incompletely specified reg property with information
from a driver configuration file. It may only be specified in a driver configuration
file.
All SBus devices must provide reg properties to the system. The first two integer elements of
the reg property are used to construct the address part
of the device name under /devices.
Only devices that generate interrupts need to provide interrupts properties.
Occasionally, it may be necessary to override or augment the configuration
information supplied by the SBus device.
This can be achieved by writing a driver configuration file that describes
a prototype device information (devinfo) node specification, containing
the additional properties required.
For the system to merge the information, certain conditions must be
met. First, the name property must be the same. Second,
either the first two integers (slot number and offset) of the two reg properties must be the same, or the second integer (offset)
of the reg and registers properties
must be the same.
In the event that the SBus card has
no reg property at all, the self-identifying information
cannot be used, so all the details of the card must be specified in a driver
configuration file.
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