bus_space(9)

NAME

bus_space, bus_space_barrier, bus_space_copy_region_1, bus_space_copy_region_2, bus_space_copy_region_4, bus_space_copy_region_8, bus_space_free, bus_space_map,
bus_space_read_1,
bus_space_read_2, bus_space_read_4, bus_space_read_8, bus_space_read_multi_1, bus_space_read_multi_2,
bus_space_read_multi_4,
bus_space_read_multi_8, bus_space_read_region_1,
bus_space_read_region_2,
bus_space_read_region_4, bus_space_read_region_8,
bus_space_set_region_1,
bus_space_set_region_2, bus_space_set_region_4,
bus_space_set_region_8,
bus_space_subregion, bus_space_unmap, bus_space_set_multi_1, bus_space_set_multi_2, bus_space_set_multi_4,
bus_space_set_multi_8,
bus_space_write_1, bus_space_write_2, bus_space_write_4, bus_space_write_8, bus_space_write_multi_1,
bus_space_write_multi_2,
bus_space_write_multi_4, bus_space_write_multi_8, bus_space_write_region_1, bus_space_write_region_2, bus_space_write_region_4, bus_space_write_region_8 - bus
space manipulation functions

SYNOPSIS

#include <machine/bus.h>
int
bus_space_map(bus_space_tag_t   space,  bus_addr_t  address,
bus_size_t size,
        int flags, bus_space_handle_t *handlep);
void
bus_space_unmap(bus_space_tag_t  space,   bus_space_handle_t
handle,
        bus_size_t size);
int
bus_space_subregion(bus_space_tag_t                   space,
bus_space_handle_t handle,
        bus_size_t offset, bus_size_t size,
        bus_space_handle_t *nhandlep);
int
bus_space_alloc(bus_space_tag_t space, bus_addr_t reg_start,
        bus_addr_t   reg_end,  bus_size_t  size,  bus_size_t
alignment,
        bus_size_t boundary, int flags, bus_addr_t *addrp,
        bus_space_handle_t *handlep);
void
bus_space_free(bus_space_tag_t   space,   bus_space_handle_t
handle,
        bus_size_t size);
u_int8_t
bus_space_read_1(bus_space_tag_t  space,  bus_space_handle_t
handle,
        bus_size_t offset);
u_int16_t
bus_space_read_2(bus_space_tag_t  space,  bus_space_handle_t
handle,
        bus_size_t offset);
u_int32_t
bus_space_read_4(bus_space_tag_t  space,  bus_space_handle_t
handle,
        bus_size_t offset);
u_int64_t
bus_space_read_8(bus_space_tag_t  space,  bus_space_handle_t
handle,
        bus_size_t offset);
void
bus_space_write_1(bus_space_tag_t  space, bus_space_handle_t
handle,
        bus_size_t offset, u_int8_t value);
void
bus_space_write_2(bus_space_tag_t space,  bus_space_handle_t
handle,
        bus_size_t offset, u_int16_t value);
void
bus_space_write_4(bus_space_tag_t  space, bus_space_handle_t
handle,
        bus_size_t offset, u_int32_t value);
void
bus_space_write_8(bus_space_tag_t space,  bus_space_handle_t
handle,
        bus_size_t offset, u_int64_t value);
void
bus_space_barrier(bus_space_tag_t  space, bus_space_handle_t
handle,
        bus_size_t offset, bus_size_t length, int flags);
void
bus_space_read_region_1(bus_space_tag_t               space,
bus_space_handle_t handle,
        bus_size_t   offset,   u_int8_t  *datap,  bus_size_t
count);
void
bus_space_read_region_2(bus_space_tag_t               space,
bus_space_handle_t handle,
        bus_size_t   offset,  u_int16_t  *datap,  bus_size_t
count);
void
bus_space_read_region_4(bus_space_tag_t               space,
bus_space_handle_t handle,
        bus_size_t   offset,  u_int32_t  *datap,  bus_size_t
count);
void
bus_space_read_region_8(bus_space_tag_t               space,
bus_space_handle_t handle,
        bus_size_t   offset,  u_int64_t  *datap,  bus_size_t
count);
void
bus_space_write_region_1(bus_space_tag_t space,
        bus_space_handle_t   handle,   bus_size_t    offset,
u_int8_t *datap,
        bus_size_t count);
void
bus_space_write_region_2(bus_space_tag_t space,
        bus_space_handle_t    handle,   bus_size_t   offset,
u_int16_t *datap,
        bus_size_t count);
void
bus_space_write_region_4(bus_space_tag_t space,
        bus_space_handle_t   handle,   bus_size_t    offset,
u_int32_t *datap,
        bus_size_t count);
void
bus_space_write_region_8(bus_space_tag_t space,
        bus_space_handle_t    handle,   bus_size_t   offset,
u_int64_t *datap,
        bus_size_t count);
void
bus_space_copy_region_1(bus_space_tag_t space,
        bus_space_handle_t srchandle, bus_size_t srcoffset,
        bus_space_handle_t dsthandle, bus_size_t dstoffset,
        bus_size_t count);
void
bus_space_copy_region_2(bus_space_tag_t space,
        bus_space_handle_t srchandle, bus_size_t srcoffset,
        bus_space_handle_t dsthandle, bus_size_t dstoffset,
        bus_size_t count);
void
bus_space_copy_region_4(bus_space_tag_t space,
        bus_space_handle_t srchandle, bus_size_t srcoffset,
        bus_space_handle_t dsthandle, bus_size_t dstoffset,
        bus_size_t count);
void
bus_space_copy_region_8(bus_space_tag_t space,
        bus_space_handle_t srchandle, bus_size_t srcoffset,
        bus_space_handle_t dsthandle, bus_size_t dstoffset,
        bus_size_t count);
void
bus_space_set_region_1(bus_space_tag_t                space,
bus_space_handle_t handle,
        bus_size_t   offset,   u_int8_t   value,  bus_size_t
count);
void
bus_space_set_region_2(bus_space_tag_t                space,
bus_space_handle_t handle,
        bus_size_t   offset,   u_int16_t  value,  bus_size_t
count);
void
bus_space_set_region_4(bus_space_tag_t                space,
bus_space_handle_t handle,
        bus_size_t   offset,   u_int32_t  value,  bus_size_t
count);
void
bus_space_set_region_8(bus_space_tag_t                space,
bus_space_handle_t handle,
        bus_size_t   offset,   u_int64_t  value,  bus_size_t
count);
void
bus_space_read_multi_1(bus_space_tag_t                space,
bus_space_handle_t handle,
        bus_size_t   offset,   u_int8_t  *datap,  bus_size_t
count);
void
bus_space_read_multi_2(bus_space_tag_t                space,
bus_space_handle_t handle,
        bus_size_t   offset,  u_int16_t  *datap,  bus_size_t
count);
void
bus_space_read_multi_4(bus_space_tag_t                space,
bus_space_handle_t handle,
        bus_size_t   offset,  u_int32_t  *datap,  bus_size_t
count);
void
bus_space_read_multi_8(bus_space_tag_t                space,
bus_space_handle_t handle,
        bus_size_t   offset,  u_int64_t  *datap,  bus_size_t
count);
void
bus_space_write_multi_1(bus_space_tag_t               space,
bus_space_handle_t handle,
        bus_size_t   offset,   u_int8_t  *datap,  bus_size_t
count);
void
bus_space_write_multi_2(bus_space_tag_t               space,
bus_space_handle_t handle,
        bus_size_t   offset,  u_int16_t  *datap,  bus_size_t
count);
void
bus_space_write_multi_4(bus_space_tag_t               space,
bus_space_handle_t handle,
        bus_size_t   offset,  u_int32_t  *datap,  bus_size_t
count);
void
bus_space_write_multi_8(bus_space_tag_t               space,
bus_space_handle_t handle,
        bus_size_t   offset,  u_int64_t  *datap,  bus_size_t
count);
void
bus_space_set_multi_1(bus_space_tag_t                 space,
bus_space_handle_t handle,
        bus_size_t   offset,   u_int8_t   value,  bus_size_t
count);
void
bus_space_set_multi_2(bus_space_tag_t                 space,
bus_space_handle_t handle,
        bus_size_t   offset,   u_int16_t  value,  bus_size_t
count);
void
bus_space_set_multi_4(bus_space_tag_t                 space,
bus_space_handle_t handle,
        bus_size_t   offset,   u_int32_t  value,  bus_size_t
count);
void
bus_space_set_multi_8(bus_space_tag_t                 space,
bus_space_handle_t handle,
        bus_size_t   offset,   u_int64_t  value,  bus_size_t
count);

DESCRIPTION

The bus_space functions exist to allow device drivers ma
chine-independent access to bus memory and register areas. All of the func
tions and types described in this document can be used by including the
#include
<machine/bus.h>
header file.
Many common devices are used on multiple architectures, but
are accessed differently on each because of architectural constraints.
For instance, a device which is mapped in one system's I/O space may be
mapped in memory space on a second system. On a third system, architec
tural limitations might change the way registers need to be accessed
(e.g. creating a non-linear register space). In some cases, a single driver
may need to access the same type of device in multiple ways in a single
system or
architecture. The goal of the bus_space functions is to al
low a single driver source file to manipulate a set of devices on differ
ent system architectures, and to allow a single driver object file to
manipulate a set of devices on multiple bus types on a single architec
ture.
Not all busses have to implement all functions described in
this document, though that is encouraged if the operations are logi
cally supported by the bus. Unimplemented functions should cause compile
time errors if possible.
All of the interface definitions described in this document
are shown as function prototypes and discussed as if they were required
to be functions. Implementations are encouraged to implement proto
typed (typechecked) versions of these interfaces, but may implement
them as macros if appropriate. Machine-dependent types, variables, and
functions should
be marked clearly in #include <machine/bus.h> to avoid confusion with the machine-independent types and
functions, and, if possible, should be given names which make the machine
dependence clear.

CONCEPTS AND GUIDELINES

Bus spaces are described by bus space tags, which can be
created only by machine-dependent code. A given machine may have several
different types of bus space (e.g. memory space and I/O space), and thus may
provide multiple different bus space tags. Individual busses or de
vices on a machine may use more than one bus space tag. For instance,
ISA devices are given an ISA memory space tag and an ISA I/O space tag.
Architectures may have several different tags which represent the
same type of space, for instance because of multiple different host bus
interface chipsets.
A range in bus space is described by a bus address and a bus
size. The bus address describes the start of the range in bus space.
The bus size describes the size of the range in bytes. Busses which are
not byte addressable may require use of bus space ranges with appro
priately aligned addresses and properly rounded sizes.
Access to regions of bus space is facilitated by use of bus
space handles, which are usually created by mapping a specific range
of a bus space. Handles may also be created by allocating and map
ping a range of bus space, the actual location of which is picked by the im
plementation within bounds specified by the caller of the allocation
function.
All of the bus space access functions require one bus space
tag argument, at least one handle argument, and at least one offset argu
ment (a bus size). The bus space tag specifies the space, each handle
specifies a region in the space, and each offset specifies the offset
into the region of the actual location(s) to be accessed. Offsets are given
in bytes, though busses may impose alignment constraints. The offset
used to access data relative to a given handle must be such that all
of the data being accessed is in the mapped region that the handle de
scribes. Trying to access data outside that region is an error.
Because some architectures' memory systems use buffering to
improve memory and device access performance, there is a mechanism
which can be used to create ``barriers'' in the bus space read and write
stream. There are three types of barriers: read, write, and read/write. All
reads started to the region before a read barrier must complete before any
reads after the read barrier are started. (The analogous requirement is
true for write barriers.) Read/write barriers force all reads and
writes started before the barrier to complete before any reads or writes
after the barrier are started. Correctly-written drivers will include
all appropriate barriers, and assume only the read/write ordering imposed by
the barrier operations.
People trying to write portable drivers with the bus_space
functions should try to make minimal assumptions about what the system
allows. In particular, they should expect that the system requires bus
space addresses being accessed to be naturally aligned (i.e., base
address of handle added to offset is a multiple of the access size),
and that the system does alignment checking on pointers (i.e., pointer to
objects being read and written must point to properly-aligned data).
The descriptions of the bus_space functions given below all
assume that they are called with proper arguments. If called with in
valid arguments or arguments that are out of range (e.g. trying to access
data outside of the region mapped when a given handle was created), unde
fined behaviour results. In that case, they may cause the system to halt,
either intentionally (via panic) or unintentionally (by causing a fatal
trap of by some other means) or may cause improper operation which is
not immediately fatal. Functions which return void or which return
data read from bus space (i.e., functions which do not obviously return an
error code) do not fail. They could only fail if given invalid argu
ments, and in that case their behaviour is undefined.

TYPES

Several types are defined in #include <machine/bus.h> to facilitate use of the bus_space functions by drivers.
bus_addr_t: The bus_addr_t type is used to describe bus addresses. It; must be an
unsigned integral type capable of holding the largest bus; address usable
by the architecture. This type is primarily used when map; ping and unmapping bus space.
bus_size_t: The bus_size_t type is used to describe sizes of ranges in; bus space. It
must be an unsigned integral type capable of holding the; size of the
largest bus address range usable on the architecture. This; type is used
by virtually all of the bus_space functions, describing; sizes when mapping regions and offsets into regions when performing space; access operations.
bus_space_tag_t: The bus_space_tag_t type is used to describe a particular; bus space on a
machine. Its contents are machine-dependent and should be; considered
opaque by machine-independent code. This type is used by; all bus_space
functions to name the space on which they are operating.
bus_space_handle_t: The bus_space_handle_t type is used to describe a mapping of; a range of
bus space. Its contents are machine-dependent and should be; considered
opaque by machine-independent code. This type is used when; performing
bus space access operations.

MAPPING AND UNMAPPING BUS SPACE

This section is specific to the NetBSD version of these
functions and may or may not apply to the FreeBSD version.
Bus space must be mapped before it can be used, and should
be unmapped
when it is no longer needed. The bus_space_map() and
bus_space_unmap()
functions provide these capabilities.
Some drivers need to be able to pass a subregion of already
mapped bus
space to another driver or module within a driver. The
bus_space_subregion() function allows such subregions to be
created.
bus_space_map(space, address, size, flags, handlep): The bus_space_map() function maps the region of bus space; named by the
space, address, and size arguments. If successful, it re; turns zero and
fills in the bus space handle pointed to by handlep with the; handle that
can be used to access the mapped region. If unsuccessful,; it will return
non-zero and leave the bus space handle pointed to by; handlep in an undefined state.; The flags argument controls how the space is to be mapped.; Supported
flags include:; BUS_SPACE_MAP_CACHEABLE Try to map the space so that; accesses can be
cached and/or prefetched by the

system. If
this flag is not specified, the

implementation should map the space so

that it will
not be cached or prefetched.

This flag must have a value of

1 on all
implementations for backward

compatibility.
BUS_SPACE_MAP_LINEAR Try to map the space so that
its contents: can be accessed linearly via; normal memory
access methods (e.g. pointer; dereferencing
and structure accesses). This; is useful
when software wants to do di; rect access to a
memory device, e.g. a frame; buffer. If this
flag is specified and linear; mapping is not
possible, the bus_space_map(); call should
fail. If this flag is not; specified, the
system may map the space in; whatever way is
most convenient.
Not all combinations of flags make sense or are supported
with all spaces. For instance, BUS_SPACE_MAP_CACHEABLE may be mean
ingless when used on many systems' I/O port spaces, and on some systems BUS_SPACE_MAP_LINEAR without BUS_SPACE_MAP_CACHEABLE may
never work. When the system hardware or firmware provides hints as to
how spaces should be mapped (e.g. the PCI memory mapping registers'
``prefetchable'' bit), those hints should be followed for maximum compatibil
ity. On some systems, requesting a mapping that cannot be satisfied (e.g.
requesting a non-cacheable mapping when the system can only provide a
cacheable one) will cause the request to fail.
Some implementations may keep track of use of bus space for
some or all bus spaces and refuse to allow duplicate allocations. This
is encouraged for bus spaces which have no notion of slot-specific space
addressing, such as ISA and VME, and for spaces which coexist with those
spaces (e.g. EISA and PCI memory and I/O spaces co-existing with ISA mem
ory and I/O spaces).
Mapped regions may contain areas for which no there is no
device on the bus. If space in those areas is accessed, the results are
bus-dependent.
bus_space_unmap(space, handle, size): The bus_space_unmap() function unmaps a region of bus space; mapped with
bus_space_map(). When unmapping a region, the size speci; fied should be
the same as the size given to bus_space_map() when mapping; that region.; After bus_space_unmap() is called on a handle, that handle; is no longer
valid. (If copies were made of the handle they are no; longer valid,
either.); This function will never fail. If it would fail (e.g. be; cause of an
argument error), that indicates a software bug which should; cause a
panic. In that case, bus_space_unmap() will never return.
bus_space_subregion(space, handle, offset, size, nhandlep): The bus_space_subregion() function is a convenience function; which makes
a new handle to some subregion of an already-mapped region; of bus space.
The subregion described by the new handle starts at byte; offset offset
into the region described by handle, with the size give by; size, and must
be wholly contained within the original region.; If successful, bus_space_subregion() returns zero and fills; in the bus
space handle pointed to by nhandlep. If unsuccessful, it; returns nonzero and leaves the bus space handle pointed to by nhandlep; in an undefined state. In either case, the handle described by handle; remains
valid and is unmodified.; When done with a handle created by bus_space_subregion(),; the handle
should be thrown away. Under no circumstances should; bus_space_unmap()
be used on the handle. Doing so may confuse any resource; management
being done on the space, and will result in undefined be; haviour. When
bus_space_unmap() or bus_space_free() is called on a handle,; all subregions of that handle become invalid.

ALLOCATING AND FREEING BUS SPACE

This section is specific to the NetBSD version of these
functions and may or may not apply to the FreeBSD version.
Some devices require or allow bus space to be allocated by
the operating system for device use. When the devices no longer need the
space, the operating system should free it for use by other devices.
The
bus_space_alloc() and bus_space_free() functions provide
these capabilities.
bus_space_alloc(space, reg_start, reg_end, size, alignment,
boundary,: flags, addrp, handlep)
The bus_space_alloc() function allocates and maps a region; of bus space
with the size given by size, corresponding to the given con; straints. If
successful, it returns zero, fills in the bus address point; ed to by addrp
with the bus space address of the allocated region, and; fills in the bus
space handle pointed to by handlep with the handle that can; be used to
access that region. If unsuccessful, it returns non-zero; and leaves the
bus address pointed to by addrp and the bus space handle; pointed to by
handlep in an undefined state.; Constraints on the allocation are given by the reg_start,; reg_end,
alignment, and boundary parameters. The allocated region; will start at
or after reg_start and end before or at reg_end. The; alignment constraint must be a power of two, and the allocated region; will start at an
address that is an even multiple of that power of two. The; boundary constraint, if non-zero, ensures that the region is allocated; so that first
address in region / boundary has the same value as last; address in region
/ boundary. If the constraints cannot be met,; bus_space_alloc() will
fail. It is an error to specify a set of constraints that; can never be
met (for example, size greater than boundary).; The flags parameter is the same as the like-named parameter; to
bus_space_map(), the same flag values should be used, and; they have the
same meanings.; Handles created by bus_space_alloc() should only be freed; with
bus_space_free(). Trying to use bus_space_unmap() on them; causes undefined behaviour. The bus_space_subregion() function can be; used on handles created by bus_space_alloc().
bus_space_free(space, handle, size): The bus_space_free() function unmaps and frees a region of; bus space
mapped and allocated with bus_space_alloc(). When unmapping; a region,
the size specified should be the same as the size given to
bus_space_alloc() when allocating the region.; After bus_space_free() is called on a handle, that handle is; no longer
valid. (If copies were made of the handle, they are no; longer valid,
either.); This function will never fail. If it would fail (e.g. be; cause of an
argument error), that indicates a software bug which should; cause a
panic. In that case, bus_space_free() will never return.

READING AND WRITING SINGLE DATA ITEMS

The simplest way to access bus space is to read or write a
single data
item. The bus_space_read_N() and bus_space_write_N() fami
lies of functions provide the ability to read and write 1, 2, 4, and 8
byte data items on busses which support those access sizes.
bus_space_read_1(space, handle, offset)
bus_space_read_2(space, handle, offset)
bus_space_read_4(space, handle, offset)
bus_space_read_8(space, handle, offset): The bus_space_read_N() family of functions reads a 1, 2, 4,; or 8 byte
data item from the offset specified by offset into the re; gion specified
by handle of the bus space specified by space. The location; being read
must lie within the bus space region specified by handle.; For portability, the starting address of the region speci; fied by handle
plus the offset should be a multiple of the size of data; item being read.
On some systems, not obeying this requirement may cause in; correct data to
be read, on others it may cause a system crash.; Read operations done by the bus_space_read_N() functions may; be executed
out of order with respect to other pending read and write; operations
unless order is enforced by use of the bus_space_barrier(); function.; These functions will never fail. If they would fail (e.g.; because of an
argument error), that indicates a software bug which should; cause a
panic. In that case, they will never return.
bus_space_write_1(space, handle, offset, value)
bus_space_write_2(space, handle, offset, value)
bus_space_write_4(space, handle, offset, value)
bus_space_write_8(space, handle, offset, value): The bus_space_write_N() family of functions writes a 1, 2,; 4, or 8 byte
data item to the offset specified by offset into the region; specified by
handle of the bus space specified by space. The location; being written
must lie within the bus space region specified by handle.; For portability, the starting address of the region speci; fied by handle
plus the offset should be a multiple of the size of data; item being written. On some systems, not obeying this requirement may; cause incorrect
data to be written, on others it may cause a system crash.; Write operations done by the bus_space_write_N() functions; may be executed out of order with respect to other pending read and; write operations unless order is enforced by use of the; bus_space_barrier() function.; These functions will never fail. If they would fail (e.g.; because of an
argument error), that indicates a software bug which should; cause a
panic. In that case, they will never return.

BARRIERS

In order to allow high-performance buffering implementations
to avoid bus activity on every operation, read and write ordering should
be specified explicitly by drivers when necessary. The
bus_space_barrier() function
provides that ability.
bus_space_barrier(space, handle, offset, length, flags): The bus_space_barrier() function enforces ordering of bus; space read and
write operations for the specified subregion (described by; the offset and
length parameters) of the region named by handle in the; space named by
space.; The flags argument controls what types of operations are to; be ordered.
Supported flags are:; BUS_SPACE_BARRIER_READ Synchronize read operations.; BUS_SPACE_BARRIER_WRITE Synchronize write operations.; Those flags can be combined (or-ed together) to enforce or; dering on both
read and write operations.; All of the specified type(s) of operation which are done to; the region
before the barrier operation are guaranteed to complete be; fore any of the
specified type(s) of operation done after the barrier.; Example: Consider a hypothetical device with two single-byte; ports, one
write-only input port (at offset 0) and a read-only output; port (at offset 1). Operation of the device is as follows: data bytes; are written to
the input port, and are placed by the device on a stack, the; top of which
is read by reading from the output port. The sequence to; correctly write
two data bytes to the device then read those two data bytes; back would
be:; /*
* t and h are the tag and handle for the mapped device's
* space.
*/; bus_space_write_1(t, h, 0, data0);
bus_space_barrier(t, h, 0, 1, BUS_SPACE_BARRIER_WRITE); /*; 1 */
bus_space_write_1(t, h, 0, data1);
bus_space_barrier(t, h, 0, 2,
BUS_SPACE_BARRIER_READ|BUS_SPACE_BARRIER_WRITE); /*

2 */; ndata1 = bus_space_read_1(t, h, 1);
bus_space_barrier(t, h, 1, 1, BUS_SPACE_BARRIER_READ); /*; 3 */
ndata0 = bus_space_read_1(t, h, 1);
/* data0 == ndata0, data1 == ndata1 */; The first barrier makes sure that the first write finishes; before the
second write is issued, so that two writes to the input port; are done in
order and are not collapsed into a single write. This en; sures that the
data bytes are written to the device correctly and in order.; The second barrier makes sure that the writes to the output; port finish
before any of the reads to the input port are issued, there; by making sure
that all of the writes are finished before data is read.; This ensures
that the first byte read from the device really is the last; one that was
written.; The third barrier makes sure that the first read finishes; before the second read is issued, ensuring that data is read correctly and; in order.; The barriers in the example above are specified to cover the; absolute
minimum number of bus space locations. It is correct (and; often easier)
to make barrier operations cover the device's whole range of; bus space,
that is, to specify an offset of zero and the size of the; whole region.

REGION OPERATIONS

Some devices use buffers which are mapped as regions in bus
space. Often, drivers want to copy the contents of those buffers to
or from memory, e.g. into mbufs which can be passed to higher levels of
the system or from mbufs to be output to a network. In order to allow
drivers to do this as efficiently as possible, the
bus_space_read_region_N() and
bus_space_write_region_N() families of functions are provid
ed.
Drivers occasionally need to copy one region of a bus space
to another, or to set all locations in a region of bus space to contain
a single
value. The bus_space_copy_region_N() family of functions
and the
bus_space_set_region_N() family of functions allow drivers
to perform these operations.
bus_space_read_region_1(space, handle, offset, datap, count)
bus_space_read_region_2(space, handle, offset, datap, count)
bus_space_read_region_4(space, handle, offset, datap, count)
bus_space_read_region_8(space, handle, offset, datap, count): The bus_space_read_region_N() family of functions reads; count 1, 2, 4, or
8 byte data items from bus space starting at byte offset; offset in the
region specified by handle of the bus space specified by; space and writes
them into the array specified by datap. Each successive da; ta item is
read from an offset 1, 2, 4, or 8 bytes after the previous; data item
(depending on which function is used). All locations being; read must lie
within the bus space region specified by handle.; For portability, the starting address of the region speci; fied by handle
plus the offset should be a multiple of the size of data; items being read
and the data array pointer should be properly aligned. On; some systems,
not obeying these requirements may cause incorrect data to; be read, on
others it may cause a system crash.; Read operations done by the bus_space_read_region_N() func; tions may be
executed in any order. They may also be executed out of or; der with
respect to other pending read and write operations unless; order is
enforced by use of the bus_space_barrier() function. There; is no way to
insert barriers between reads of individual bus space loca; tions executed
by the bus_space_read_region_N() functions.; These functions will never fail. If they would fail (e.g.; because of an
argument error), that indicates a software bug which should; cause a
panic. In that case, they will never return.
bus_space_write_region_1(space, handle, offset, datap, count)
bus_space_write_region_2(space, handle, offset, datap, count)
bus_space_write_region_4(space, handle, offset, datap, count)
bus_space_write_region_8(space, handle, offset, datap, count): The bus_space_write_region_N() family of functions reads; count 1, 2, 4,
or 8 byte data items from the array specified by datap and; writes them to
bus space starting at byte offset offset in the region spec; ified by
handle of the bus space specified by space. Each successive; data item is
written to an offset 1, 2, 4, or 8 bytes after the previous; data item
(depending on which function is used). All locations being; written must
lie within the bus space region specified by handle.; For portability, the starting address of the region speci; fied by handle
plus the offset should be a multiple of the size of data; items being
written and the data array pointer should be properly; aligned. On some
systems, not obeying these requirements may cause incorrect; data to be
written, on others it may cause a system crash.; Write operations done by the bus_space_write_region_N(); functions may be
executed in any order. They may also be executed out of or; der with
respect to other pending read and write operations unless; order is
enforced by use of the bus_space_barrier() function. There; is no way to
insert barriers between writes of individual bus space loca; tions executed
by the bus_space_write_region_N() functions.; These functions will never fail. If they would fail (e.g.; because of an
argument error), that indicates a software bug which should; cause a
panic. In that case, they will never return.
bus_space_copy_region_1(space, srchandle, srcoffset,
dsthandle, dstoffset,: count)
bus_space_copy_region_2(space, srchandle, srcoffset,
dsthandle, dstoffset,: count)
bus_space_copy_region_4(space, srchandle, srcoffset,
dsthandle, dstoffset,: count)
bus_space_copy_region_8(space, srchandle, srcoffset,
dsthandle, dstoffset,: count)
The bus_space_copy_region_N() family of functions copies; count 1, 2, 4,
or 8 byte data items in bus space from the area starting at; byte offset
srcoffset in the region specified by srchandle of the bus; space specified
by space to the area starting at byte offset dstoffset in; the region
specified by dsthandle in the same bus space. Each succes; sive data item
read or written has an offset 1, 2, 4, or 8 bytes after the; previous data
item (depending on which function is used). All locations; being read and
written must lie within the bus space region specified by; their respective handles.; For portability, the starting addresses of the regions spec; ified by the
each handle plus its respective offset should be a multiple; of the size
of data items being copied. On some systems, not obeying; this requirement may cause incorrect data to be copied, on others it may; cause a system crash.; Read and write operations done by the; bus_space_copy_region_N() functions may be executed in any order. They may also be executed out; of order
with respect to other pending read and write operations un; less order is
enforced by use of the bus_space_barrier(function). There; is no way to
insert barriers between reads or writes of individual bus; space locations
executed by the bus_space_copy_region_N() functions.; Overlapping copies between different subregions of a single; region of bus
space are handled correctly by the bus_space_copy_region_N(); functions.; These functions will never fail. If they would fail (e.g.; because of an
argument error), that indicates a software bug which should; cause a
panic. In that case, they will never return.
bus_space_set_region_1(space, handle, offset, value, count)
bus_space_set_region_2(space, handle, offset, value, count)
bus_space_set_region_4(space, handle, offset, value, count)
bus_space_set_region_8(space, handle, offset, value, count): The bus_space_set_region_N() family of functions writes the; given value
to count 1, 2, 4, or 8 byte data items in bus space starting; at byte offset offset in the region specified by handle of the bus; space specified
by space. Each successive data item has an offset 1, 2, 4,; or 8 bytes
after the previous data item (depending on which function is; used). All
locations being written must lie within the bus space region; specified by
handle.; For portability, the starting address of the region speci; fied by handle
plus the offset should be a multiple of the size of data; items being
written. On some systems, not obeying this requirement may; cause incorrect data to be written, on others it may cause a system; crash.; Write operations done by the bus_space_set_region_N() func; tions may be
executed in any order. They may also be executed out of or; der with
respect to other pending read and write operations unless; order is
enforced by use of the bus_space_barrier() function. There; is no way to
insert barriers between writes of individual bus space loca; tions executed
by the bus_space_set_region_N() functions.; These functions will never fail. If they would fail (e.g.; because of an
argument error), that indicates a software bug which should; cause a
panic. In that case, they will never return.

READING AND WRITING A SINGLE LOCATION MULTIPLE TIMES

Some devices implement single locations in bus space which
are to be read or written multiple times to communicate data, e.g. some
ethernet devices' packet buffer FIFOs. In order to allow drivers to
manipulate
these types of devices as efficiently as possible, the
bus_space_read_multi_N(), bus_space_set_multi_N(), and bus_space_write_multi_N() families of functions are provid
ed.
bus_space_read_multi_1(space, handle, offset, datap, count)
bus_space_read_multi_2(space, handle, offset, datap, count)
bus_space_read_multi_4(space, handle, offset, datap, count)
bus_space_read_multi_8(space, handle, offset, datap, count): The bus_space_read_multi_N() family of functions reads count; 1, 2, 4, or
8 byte data items from bus space at byte offset offset in; the region
specified by handle of the bus space specified by space and; writes them
into the array specified by datap. Each successive data; item is read
from the same location in bus space. The location being; read must lie
within the bus space region specified by handle.; For portability, the starting address of the region speci; fied by handle
plus the offset should be a multiple of the size of data; items being read
and the data array pointer should be properly aligned. On; some systems,
not obeying these requirements may cause incorrect data to; be read, on
others it may cause a system crash.; Read operations done by the bus_space_read_multi_N() func; tions may be
executed out of order with respect to other pending read and; write operations unless order is enforced by use of the; bus_space_barrier() function. Because the bus_space_read_multi_N() functions read; the same bus
space location multiple times, they place an implicit read; barrier
between each successive read of that bus space location.; These functions will never fail. If they would fail (e.g.; because of an
argument error), that indicates a software bug which should; cause a
panic. In that case, they will never return.
bus_space_write_multi_1(space, handle, offset, datap, count)
bus_space_write_multi_2(space, handle, offset, datap, count)
bus_space_write_multi_4(space, handle, offset, datap, count)
bus_space_write_multi_8(space, handle, offset, datap, count): The bus_space_write_multi_N() family of functions reads; count 1, 2, 4, or
8 byte data items from the array specified by datap and; writes them into
bus space at byte offset offset in the region specified by; handle of the
bus space specified by space. Each successive data item is; written to
the same location in bus space. The location being written; must lie
within the bus space region specified by handle.; For portability, the starting address of the region speci; fied by handle
plus the offset should be a multiple of the size of data; items being
written and the data array pointer should be properly; aligned. On some
systems, not obeying these requirements may cause incorrect; data to be
written, on others it may cause a system crash.; Write operations done by the bus_space_write_multi_N() func; tions may be
executed out of order with respect to other pending read and; write operations unless order is enforced by use of the; bus_space_barrier() function. Because the bus_space_write_multi_N() functions write; the same bus
space location multiple times, they place an implicit write; barrier
between each successive write of that bus space location.; These functions will never fail. If they would fail (e.g.; because of an
argument error), that indicates a software bug which should; cause a
panic. In that case, they will never return.
bus_space_set_multi_1(space, handle, offset, value, count)
bus_space_set_multi_2(space, handle, offset, value, count)
bus_space_set_multi_4(space, handle, offset, value, count)
bus_space_set_multi_8(space, handle, offset, value, count): The bus_space_set_multi_N() writes value into bus space at; byte offset
offset in the region specified by handle of the bus space; specified by
space, count times. The location being written must lie; within the bus
space region specified by handle.; For portability, the starting address of the region speci; fied by handle
plus the offset should be a multiple of the size of data; items being
written and the data array pointer should be properly; aligned. On some
systems, not obeying these requirements may cause incorrect; data to be
written, on others it may cause a system crash.; Write operations done by the bus_space_set_multi_N() func; tions may be
executed out of order with respect to other pending read and; write operations unless order is enforced by use of the; bus_space_barrier() function. Because the bus_space_set_multi_N() functions write; the same bus
space location multiple times, they place an implicit write; barrier
between each successive write of that bus space location.; These functions will never fail. If they would fail (e.g.; because of an
argument error), that indicates a software bug which should; cause a
panic. In that case, they will never return.

COMPATIBILITY

The current NetBSD version of the bus_space interface speci
fication differs slightly from the original specification that came into
wide use and FreeBSD adopted. A few of the function names and arguments
have changed for consistency and increased functionality.

HISTORY

The bus_space functions were introduced in a different form
(memory and I/O spaces were accessed via different sets of functions) in
NetBSD 1.2. The functions were merged to work on generic ``spaces'' ear
ly in the NetBSD 1.3 development cycle, and many drivers were convert
ed to use them. This document was written later during the NetBSD 1.3
development cycle, and the specification was updated to fix some consis
tency problems and to add some missing functionality.
The manual page was then adopted to the version of the in
terface that FreeBSD imported for the CAM SCSI drivers, plus subsequent
evolution.
The FreeBSD bus_space version was imported in FreeBSD 3.0.

AUTHORS

The bus_space interfaces were designed and implemented by
the NetBSD developer community. Primary contributors and implementors
were Chris Demetriou, Jason Thorpe, and Charles Hannum, but the rest of
the NetBSD developers and the user community played a significant role
in development.
Justin Gibbs ported these interfaces to FreeBSD.
Chris Demetriou wrote this manual page.
Warner Losh modified it for the FreeBSD implementation.

BUGS

This manual may not completely and accurately document the
interface, and many parts of the interface are unspecified.
BSD June 13, 2005

docs.sk

comprehensive documentation repository

See also

bus_space(9)

NAME

SYNOPSIS

DESCRIPTION

CONCEPTS AND GUIDELINES

TYPES

MAPPING AND UNMAPPING BUS SPACE

ALLOCATING AND FREEING BUS SPACE

READING AND WRITING SINGLE DATA ITEMS

BARRIERS

REGION OPERATIONS

READING AND WRITING A SINGLE LOCATION MULTIPLE TIMES

COMPATIBILITY

SEE ALSO

HISTORY

AUTHORS

BUGS