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.\" Written by: John H. Baldwin <jhb@FreeBSD.org>
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.Dd March 13, 2024
.Dt BUS_ADJUST_RESOURCE 9
.Os
.Sh NAME
.Nm bus_adjust_resource
.Nd adjust resource allocated from a parent bus
.Sh SYNOPSIS
.In sys/param.h
.In sys/bus.h
.Pp
.In machine/bus.h
.In sys/rman.h
.In machine/resource.h
.Ft int
.Fo bus_adjust_resource
.Fa "device_t dev" "struct resource *r"
.Fa "rman_res_t start" "rman_res_t end"
.Fc
.Sh DESCRIPTION
This function is used to ask the parent bus to adjust the resource range
assigned to an allocated resource.
The resource
.Fa r
should have been allocated by a previous call to
.Xr bus_alloc_resource 9 .
The new resource range must overlap the existing range of
.Fa r .
.Pp
Note that none of the constraints of the original allocation request such
as alignment or boundary restrictions are checked by
.Fn bus_adjust_resource .
It is the caller's responsibility to enforce any such requirements.
.Sh RETURN VALUES
The
.Fn bus_adjust_resource
method returns zero on success or an error code on failure.
.Sh EXAMPLES
Grow an existing memory resource by 4096 bytes.
.Bd -literal
	struct resource *res;
	int error;

	error = bus_adjust_resource(dev, res, rman_get_start(res),
	    rman_get_end(res) + 0x1000);
.Ed
.Sh ERRORS
.Fn bus_adjust_resource
will fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
The
.Fa dev
device does not have a parent device.
.It Bq Er EINVAL
The
.Fa r
resource is a shared resource.
.It Bq Er EINVAL
The new address range does not overlap with the existing address range of
.Fa r .
.It Bq Er EBUSY
The new address range conflicts with another allocated resource.
.El
.Sh SEE ALSO
.Xr bus_alloc_resource 9 ,
.Xr bus_release_resource 9 ,
.Xr device 9 ,
.Xr driver 9