.TH DTOVERLAY 1
.
.SH NAME
dtoverlay \- load a device-tree overlay
.
.
.SH SYNOPSIS
.SY dtoverlay
.OP \-d dir
.OP \-p string
.OP \-v
.OP \-D
.OP \-r
.OP \-R
.OP \-l
.OP \-a
.RI [ overlay " [" param=val \|.\|.\|.]]
.YS
.
.SY dtoverlay
.B \-h
.RI [ overlay " [" param ]]
.YS
.
.
.SH DESCRIPTION
.B dtoverlay
is a command line utility for manipulating the system's runtime device-tree by
adding or removing overlays.
It can also customize the base device-tree or overlays by setting parameters
within them.
See
.B [DTREE]
for more information.
.
.PP
By default, without the
.B -r
or
.B -R
options, the application adds the specified overlay. Manipulation of
active device-tree overlays usually requires root privileges.
.
.
.SH OPTIONS
.
.TP
.BR \-a
Lists all defined device-tree overlays, placing a "*" next to those that are
currently loaded.
.
.TP
.BR \-d " \fIdir\fR"
Specifies an alternate location path from which to load overlays. The utility
defaults to "/boot/overlays" or "/flash/overlays".
.
.TP
.BR \-D
Dry-run; prepares the specified overlay but doesn't apply it. The resulting
prepared overlay is saved as "dry-run.dtbo".
.
.TP
.BR \-h [\fIoverlay\fR] [\fIparam\fR]
If given without
.I overlay
or
.I param
displays help on the application overall. If
.I overlay
is specified, prints help on that overlay. Finally, if
.I param
is also specified, prints help on that parameter of the overlay. To query
parameters on the base overlay, specify "dtparam" as the
.IR overlay .
.
.TP
.BR \-l
Lists all currently loaded device-tree overlays, in the order they were loaded.
This also specifies the index of each overlay.
.
.TP
.BR \-p " \fIstring\fR"
Override the platform's "compatible" string, normally read from
"/proc/device-tree/compatible". This is used with the overlay map to determine
which platform-specific overlay to read (if necessary).
.
.TP
.BR \-r
Remove overlay. With this option, the utility will remove the specified
overlay. If no overlay is given, the last overlay loaded will be removed.
Overlays can be specified by name or by index.
.
.TP
.BR \-R
Remove the specified overlay, and all subsequent overlays that were loaded
after it. If no overlay is given, all overlays will be removed. Overlays can
be specified by name or by index.
.
.TP
.BR \-v
Verbose operation; the utility will produce more output.
.
.
.SH EXAMPLES
.
.TP
.B sudo dtoverlay w1-gpio
Load the w1-gpio overlay (to enable Dallas 1-Wire on GPIO4). Note that root
privileges are usually required for manipulating the device-tree overlays
(hence, sudo in the example).
.
.TP
.B dtoverlay -l
Show the loaded overlays.
.
.TP
.B sudo dtoverlay -r
Remove the last loaded overlay.
.
.TP
.B sudo dtoverlay gpio-shutdown gpio_pin=7 active_low=0 gpio_pull=down
Load the gpio-shutdown overlay specifying that it should pull GPIO7 down and
monitor it for a rising edge to initiate shutdown.
.
.TP
.B dtoverlay -h gpio-shutdown
Display help for the gpio-shutdown overlay
.
.TP
.B sudo dtoverlay -r gpio-shutdown
Remove the gpio-shutdown overlay, wherever it is in the load order.
.
.
.SH HOOKS
.B dtoverlay
attempts to call two executables (shell scripts by default) during its
operation:
.B dtoverlay-pre
prior to making device-tree modifications, and
.B dtoverlay-post
afterwards. Each executable is optional and will be ignored if not present.
.
.
.SH SEE ALSO
.BR dtparam (1),
.BR dtmerge (1),
.B [DTREE]
.
.
.SH REFERENCES
.TP
.B [DTREE]
https://www.raspberrypi.org/documentation/configuration/device-tree.md