xref: /illumos-gate/usr/src/man/man9f/bitset64.9f (revision 71815ce76261aa773c97600750fdce92334d1990)

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.\" Copyright 2022 Oxide Computer Company
.\"
.Dd April 12, 2022
.Dt BITSET64 9F
.Os
.Sh NAME
.Nm bitset8 ,
.Nm bitset16 ,
.Nm bitset32 ,
.Nm bitset64
.Nd set bitfield values in an integer
.Sh SYNOPSIS
.In sys/bitext.h
.Ft uint8_t
.Fo bitset8
.Fa "uint8_t base"
.Fa "uint_t high"
.Fa "uint_t low"
.Fa "uint8_t value"
.Fc
.Ft uint16_t
.Fo bitset16
.Fa "uint16_t base"
.Fa "uint_t high"
.Fa "uint_t low"
.Fa "uint16_t value"
.Fc
.Ft uint32_t
.Fo bitset32
.Fa "uint32_t base"
.Fa "uint_t high"
.Fa "uint_t low"
.Fa "uint32_t value"
.Fc
.Ft uint64_t
.Fo bitset64
.Fa "uint64_t base"
.Fa "uint_t high"
.Fa "uint_t low"
.Fa "uint64_t value"
.Fc
.Sh INTERFACE LEVEL
.Sy Volatile -
This interface is still evolving in illumos.
API and ABI stability is not guaranteed.
.Sh PARAMETERS
.Bl -tag -width Fa
.It Fa base
The starting integer that will have a value ORed into it.
.It Fa high
The high end, inclusive, of the bit range to insert
.Fa value
into
.Fa base .
.It Fa low
The low end, inclusive, of the bit range to extract from
.Fa value .
.It Fa value
A value to insert into
.Fa base .
.El
.Sh DESCRIPTION
The
.Fn bitset8 ,
.Fn bitset16 ,
.Fn bitset32 ,
and
.Fn bitset64
functions are used to logically bitwise-OR in the integer
.Fa value
into a specified bit position in
.Fa base .
Effectively, the function zeros out the bit range in
.Fa base ,
described by
.Fa high
and
.Fa low
and then performs a bitwise-OR of
.Fa base
which has been adjusted to start at
.Fa low .
.Pp
The
.Fa high
and
.Fa low
arguments describe an inclusive bit range
.Po
.Pf [ Fa low ,
.Fa high ]
.Pc
which describes where
.Fa value
should be inserted.
It is illegal
for
.Fa low
to be greater than
.Fa high ,
for
.Fa low
or
.Fa high
to exceed the integer's bit range
.Po
e.g. neither can be greater than 7 for
.Fn bitset8
.Pc ,
and
.Fa value
must not exceed the described bit range.
That is, if
.Fa high
was 2
and
.Fa low
was 1,
.Fa value
could not be larger than a 2-bit value.
.Pp
Note, these functions do not modify either
.Fa base
or
.Fa value .
.Sh RETURN VALUES
Upon successful completion, the
.Fn bitset8 ,
.Fn bitset16 ,
.Fn bitset32 ,
and
.Fn bitset64
functions all return a new value that has first cleared the specified
bit range from
.Fa base
and then replaced it with
.Fa value .
.Sh EXAMPLES
.Sy Example 1 -
Using the
.Fn bitset32
function to build up a register value.
.Pp
A common use case for these functions is to help deal with registers
that are defined as a series of bit values.
The following example shows a register's bit definitions and then how
they are used to construct a value to write.
.Bd -literal
/*
 * This represents a token register definition. It is normally a
 * uint32_t.
 */
#define	DF_IO_BASE_V2_SET_BASE(r, v)	bitx32(r, 24, 12, v)
#define	DF_IO_BASE_V2_SET_IE(r, v)	bitset32(r, 5, 5, v)
#define	DF_IO_BASE_V2_SET_WE(r, v)	bitset32(r, 1, 1, v)
#define	DF_IO_BASE_V2_SET_RE(r, v)	bitset32(r, 0, 0, v)

void
setup_register(uint32_t base)
{
	uint32_t reg = 0;

	/*
	 * Set read enable, write enable, and the base. Then write the
	 * hardware register.
	 */
	reg = DF_IO_BASE_V2_SET_RE(reg, 1);
	reg = DF_IO_BASE_V2_SET_WE(reg, 1);
	reg = DF_IO_BASE_V2_SET_BASE(reg, base);
	write_register(XXX, reg);
}
.Ed
.Sh SEE ALSO
.Xr bitdel64 9F ,
.Xr bitx64 9F