hammer2 - Allow simple 'mount @label <target>' shortcut for snapshots

[dragonfly.git] / lib / libdevinfo / devinfo.3

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.\" $FreeBSD: src/lib/libdevinfo/devinfo.3,v 1.11 2006/09/17 21:27:35 ru Exp $
.\"
.Dd September 30, 2008
.Dt DEVINFO 3
.Os
.Sh NAME
.Nm devinfo ,
.Nm devinfo_init ,
.Nm devinfo_free ,
.Nm devinfo_handle_to_device ,
.Nm devinfo_handle_to_resource ,
.Nm devinfo_handle_to_rman ,
.Nm devinfo_foreach_device_child ,
.Nm devinfo_foreach_device_resource ,
.Nm devinfo_foreach_rman_resource ,
.Nm devinfo_foreach_rman
.Nd device and resource information utility library
.Sh LIBRARY
.Lb libdevinfo
.Sh SYNOPSIS
.In devinfo.h
.Ft int
.Fn devinfo_init "void"
.Ft void
.Fn devinfo_free "void"
.Ft struct devinfo_dev *
.Fn devinfo_handle_to_device "devinfo_handle_t handle"
.Ft struct devinfo_res *
.Fn devinfo_handle_to_resource "devinfo_handle_t handle"
.Ft struct devinfo_rman *
.Fn devinfo_handle_to_rman "devinfo_handle_t handle"
.Ft int
.Fo devinfo_foreach_device_child
.Fa "struct devinfo_dev *parent"
.Fa "int (*fn)(struct devinfo_dev *child, void *arg)"
.Fa "void *arg"
.Fc
.Ft int
.Fo devinfo_foreach_device_resource
.Fa "struct devinfo_dev *dev"
.Fa "int (*fn)(struct devinfo_dev *dev, \:struct devinfo_res *res, \:void *arg)"
.Fa "void *arg"
.Fc
.Ft int
.Fo devinfo_foreach_rman_resource
.Fa "struct devinfo_rman *rman"
.Fa "int (*fn)(struct devinfo_res *res, void *arg)"
.Fa "void *arg"
.Fc
.Ft int
.Fo devinfo_foreach_rman
.Fa "int (*fn)(struct devinfo_rman *rman, void *arg)"
.Fa "void *arg"
.Fc
.Sh DESCRIPTION
The
.Nm
library provides access to the kernel's internal device hierarchy
and to the I/O resource manager.
The library uses a
.Xr sysctl 3
interface to obtain a snapshot of the kernel's state,
which is then made available to the application.
.Pp
Due to the fact that the information may be logically arranged
in a number of different fashions,
the library does not attempt to impose any structure on the data.
.Pp
Device, resource, and resource manager information is returned in
data structures defined in
.In devinfo.h :
.Bd -literal -offset indent
struct devinfo_dev {
    devinfo_handle_t    dd_handle;      /* device handle */
    devinfo_handle_t    dd_parent;      /* parent handle */
    char                *dd_name;       /* name of device */
    char                *dd_desc;       /* device description */
    char                *dd_drivername; /* name of attached driver */
    char                *dd_pnpinfo;    /* pnp info from parent bus */
    char                *dd_location;   /* Where bus thinks dev at */
    uint32_t            dd_devflags;    /* API flags */
    uint16_t            dd_flags;       /* internal dev flags */
    device_state_t      dd_state;       /* attachment state of dev */
};

struct devinfo_rman {
    devinfo_handle_t    dm_handle;      /* resource manager handle */
    u_long              dm_start;       /* resource start */
    u_long              dm_size;        /* resource size */
    char                *dm_desc;       /* resource description */
};

struct devinfo_res {
    devinfo_handle_t    dr_handle;      /* resource handle */
    devinfo_handle_t    dr_rman;        /* resource manager handle */
    devinfo_handle_t    dr_device;      /* owning device */
    u_long              dr_start;       /* region start */
    u_long              dr_size;        /* region size */
};
.Ed
.Pp
The
.Vt devinfo_handle_t
values can be used to look up the correspondingly referenced structures.
.Pp
.Fn devinfo_init
takes a snapshot of the kernel's internal device and resource state.
It returns nonzero
if after a number of retries a consistent snapshot cannot be obtained.
.Fn devinfo_init
must be called before any other functions can be used.
.Pp
.Fn devinfo_free
releases the memory associated with the snapshot.
Any pointers returned by other functions are invalidated by this,
and
.Fn devinfo_init
must be called again before using any other functions.
.Pp
.Fn devinfo_handle_to_device ,
.Fn devinfo_handle_to_resource
and
.Fn devinfo_handle_to_rman
return pointers to
.Vt devinfo_dev ,
.Vt devinfo_res
and
.Vt devinfo_rman
structures respectively based on the
.Vt devinfo_handle_t
passed to them.
These functions can be used to traverse the tree from any node to any
other node.
If
.Fn devinfo_handle_to_device
is passed the constant
.Dv DEVINFO_ROOT_DEVICE
it will return the handle to the root of the device tree.
.Pp
.Fn devinfo_foreach_device_child
invokes its callback argument
.Fa fn
on every device which is an immediate child of
.Fa device .
The
.Fa fn
function is also passed
.Fa arg ,
allowing state to be passed to the callback function.
If
.Fa fn
returns a nonzero error value the traversal is halted,
and
.Fn devinfo_foreach_device_child
returns the error value to its caller.
.Pp
.Fn devinfo_foreach_device_resource
invokes its callback argument
.Fa fn
on every resource which is owned by
.Fa device .
The
.Fa fn
function is also passed
.Fa device
and
.Fa arg ,
allowing state to be passed to the callback function.
If
.Fa fn
returns a nonzero error value the traversal is halted,
and
.Fn devinfo_foreach_device_resource
returns the error value to its caller.
.Pp
.Fn devinfo_foreach_rman_resource
invokes its callback argument
.Fa fn
on every resource within the resource manager
.Fa rman .
The
.Fa fn
function is also passed
.Fa arg ,
allowing state to be passed to the callback function.
If
.Fa fn
returns a nonzero error value the traversal is halted,
and
.Fn devinfo_foreach_rman_resource
returns the error value to its caller.
.Pp
.Fn devinfo_foreach_rman
invokes its callback argument
.Fa fn
on every resource manager.
The
.Fa fn
function is also passed
.Fa arg ,
allowing state to be passed to the callback function.
If
.Fa fn
returns a nonzero error value the traversal is halted,
and
.Fn devinfo_foreach_rman
returns the error value to its caller.
.Sh SEE ALSO
.Xr devstat 3
.Sh HISTORY
The
.Nm
library first appeared in
.Fx 5.0
and was imported into
.Dx 2.1 .
.Sh AUTHORS
.An Michael Smith Aq Mt msmith@FreeBSD.org
.Sh BUGS
This is the first implementation of the library,
and the interface is still subject to refinement.
.Pp
The interface does not report device classes or drivers,
making it hard to sort by class or driver.