FDI(5) File Formats and Configurations FDI(5)
NAME
fdi - HAL device information file format
SYNOPSIS
/usr/share/lib/xml/dtd/fdi.dtd.1
DESCRIPTION
The hardware abstraction layer facility, described in
hal(7), uses an
XML-based file format to merge arbitrary properties onto device
objects. The way device information files works is that once all
physical properties are merged onto a device object, it is tried
against the set of installed device information files. Device
information files are used for both merging facts and policy settings
for devices.
Each device information file has a number of match directives that
are tested against the properties of the device object. The
directives have the form:
<match key="property" [string|int|bool|..]="value">
If all the match directives pass, then the device information can
include the following property directives in the form:
<[merge|append|prepend] key="property" type="[string|int|bool|..]">
These directives are used to merge new properties or append to
existing properties on the device object. Any previously property
stemming from device detection can be overridden by a device
information file.
The
match,
merge,
append, and
prepend directives require that the key
attribute be either a property name on the device object in question
or a path to a property on another device object. The path to a
property is expressed either through direct specification of the
UDI,
such as
/org/freedesktop/Hal/devices/computer:foo.bar or through
indirect references such as "
@info.parent:baz", meaning that the
device object specified by the
UDI in the string property
"
info.parent" should be used to query the property "
baz". It is also
possible to use multiple indirections. For example, for a volume on a
USB memory stick, the indirection
"
@block.storage_device:@storage.physical_device:usb.vendor_id"
references the "
usb.vendor_id" property on the device object
representing the
USB interface.
When the property to match has been determined, the following
attributes can be used within the "
match" tag:
string Match a string property. For example, <match key=
"foo.bar" string="baz"> matches only if "
foo.bar"
is a string property assuming the value "
baz".
int Match an integer property
uint64 Match property with the 64-bit unsigned type
bool Match a boolean property
double Match a property of type double
exists Used as <match key="foo.bar" exists="true">. This
attribute can be used with "true" and "false",
respectively to match when a property exists or
does not exist.
empty This attribute can only be used on string
properties with "true" and "false". The
semantics for "true" is to match only when the
string is non-empty.
is_absolute_path Matches only when a string property represents an
absolute path (the path does not have to exist).
This attribute can be can be used with "true" or
"false".
is_ascii Matches only when a string property contains
ASCII characters. This attribute can be used with
"true" or "false".
compare_lt This attribute can be used with
int,
uint64,
double and
string properties to compare with a
constant. It matches when the given property is
less than the given constant using the default
ordering.
compare_le Similar to
compare_lt, but matches when the given
property is less than or equal than the given
constant using the default ordering.
compare_gt Similar to
compare_lt, but matches when the given
property is greater than the given constant using
the default ordering.
Similar to
compare_lt, but matches when the given
property is greater than or equal than the given
constant using the default ordering.
This attribute can only be used with
string and
strlist (string list). For a string key, this
matches when the property contains the given
(sub)string. For a string list, this matches if
the given string matches a item in the list.
contains_ncase Similar to
contains, but the property and the
given key are converted to lowercase before it is
checked.
The
merge,
append, and
prepend directives all require the attribute
type which specifies what is to be merged. The following values are
supported:
string The value is copied to the property. For example,
<merge key="foo bar" type="string"> baz</merege>
merges the value "baz" into the property "foo.bar".
strlist For
merge, the value is copied to the property and
the current property is overwritten. For
append and
prepend, the value is appended or prepended to the
list as a new item.
bool This attribute can merge the values "true" or
"false"
int Merges an integer
uint64 Merges an unsigned 64-bit integer
double Merges a double precision floating point number
copy_property Copies the value of a given property; supports paths
with direct and indirect UDI's. For example, <merge
key="foo.bar"
type="copy_property">@info.parent:baz.bat</merge>
merges the value of the property "baz.bat" on the
device object with the
UDI from the property
"info.parent" into the property "foo.bar" on the
device object being processed.
The
remove directive requires only a key and can be used with all
keys. For
strlist, there is also a special syntax to remove a item
from the string list. For example, to remove item "bla" from property
"foo.bar", use the following syntax:
<remove key="foo.bar" type="strlist">bla</merge>
Device Information files are stored in the following standard
hierarchy with the following default top level directories
information,
policy and
preprobe:
information Device information files to merge device information.
10freedesktop Device information files included
with the
hal tarball.
20thirdparty Device information files from the
device manufacturer and installed
from media accompanying the hardware.
30user Device information for specific
devices.
policy Device information files to merge policy properties.
10osvendor Device information files included with
the hal tarball and supplied by the
operating system vendor for policy
rules.
20thirdparty Policy rules from the device
manufacturer and installed from media
accompanying the hardware.
30user Policy rules for specific devices.
preprobe Device information files to merge information before
probe devices.
10osvendor Device information files included with
the
hal tarball and supplied by the
operating system vendor.
20thirdparty Device information files from the
device manufacturer and installed from
media accompanying the hardware.
30user Device information for specific
devices.
All device information files are matched for every
hal device object.
ATTRIBUTES
See
attributes(7) for descriptions of the following attributes:
+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Interface Stability | Volatile |
+--------------------+-----------------+
SEE ALSO
attributes(7),
hal(7),
locale(7),
smf(7),
hald(8) April 9, 2016 FDI(5)
