Reference via label allows extending nodes with compile-time checking of
whether the node being extended exists. This is useful to catch
renamed/removed nodes after an update of the device trees to be extended.
In absence of labels in the original device trees, new style path
references can be used:
/* upstream device tree */
/ {
leds: some-non-standard-led-controller-name {
led-0 {
default-state = "off";
};
};
};
/* downstream device tree */
&{/some-non-standard-led-controller-name/led-0} {
default-state = "on";
};
This is a common theme within the barebox bootloader[0], which extends the
upstream (Linux) device trees in that manner. The downside is that,
especially for deep nodes, these references can get quite long and tend to
break often due to upstream rework (e.g. rename to adhere to bindings).
Often there is a label a level or two higher that could be used. This
patch allows combining both a label and a new style path reference to
get a compile-time-checked reference, which allows rewriting the
previous downstream device tree snippet to:
&{leds/led-0} {
default-state = "on";
};
This won't be broken when /some-non-standard-led-controller-name is
renamed or moved while keeping the label. And if led-0 is renamed, we
will get the expected compile-time error.
Overlay support is skipped for now as they require special support: The
label and relative path parts need to be resolved at overlay apply-time,
not at compile-time.
[0]: https://www.barebox.org/doc/latest/devicetree/index.html
Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Prevent undefined behavior when shifting by a number that's bigger than
or equal to the width of the first operand.
Signed-off-by: Andrei Ziureaev <andrei.ziureaev@arm.com>
Message-Id: <20200714154542.18064-2-andrei.ziureaev@arm.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Use -b to explicitly set file prefix, so that byacc generates files with
the same names as bison.
Add %locations to dtc-parser.y to explicitly enable location tracking
for byacc, and define YYERROR_CALL to prevent byacc from defining it to
call yyerror with 2 parameters because of the locations directive,
because dtc-parser.y defines yyerror to accept one parameter.
Signed-off-by: Ethan Sommer <e5ten.arch@gmail.com>
Message-Id: <20191029162619.32561-1-e5ten.arch@gmail.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Replace instances of GPLv2 or later boilerplate with SPDX tags.
Signed-off-by: Rob Herring <robh@kernel.org>
Message-Id: <20190620211944.9378-2-robh@kernel.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Extend the parser to record positions, in build_node,
build_node_delete, and build_property.
srcpos structures are added to the property and node types, and to the
parameter lists of the above functions that construct these types.
Nodes and properties that are created by the compiler rather than from
parsing source code have NULL as the srcpos value.
merge_nodes, defined in livetree.c, uses srcpos_extend to combine
multiple positions, resulting in a list of positions. srcpos_extend
is defined in srcpos.c. New elements are added at the end. This
requires the srcpos type, define in srcpos.h, to be a list structure
with a next field. This next field is initialized to NULL in
srcpos.h, in the macro YYLLOC_DEFAULT invoked implicitly by the
generated parser code.
Another change to srcpos.c is to make srcpos_copy always do a full
copy, including a copy of the file substructure. This is required
because when dtc is used on the output of cpp, the successive detected
file names overwrite the file name in the file structure. The next
field does not need to be deep copied, because it is always NULL when
srcpos_copy is called; an assert checks for this. File names are only
updated in uncopied position structures.
Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
This reverts commit baa1d2cf78.
Turns out this introduced memory badness. valgrind picks it up on
x86, but it straight out SEGVs on x86.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Extend the parser to record positions, in build_node, build_node_delete,
and build_property.
srcpos structures are added to the property and node types, and to the
parameter lists of the above functions that construct these types.
Nodes and properties that are created by the compiler rather than from
parsing source code have NULL as the srcpos value.
merge_nodes, defined in livetree.c, uses srcpos_extend to combine
multiple positions, resulting in a list of positions. srcpos_extend is
defined in srcpos.c. New elements are added at the end. The srcpos
type, define in srcpos.h, is now a list structure with a next field.
Another change to srcpos.c is to make srcpos_copy always do a full copy,
including a copy of the file substructure. This is required because
when dtc is used on the output of cpp, the successive detected file
names overwrite the file name in the file structure. The next field
does not need to be deep copied, because it is only updated in newly
copied positions and the positions to which it points have also been
copied. File names are only updated in uncopied position structures.
Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
This change makes sure that nodes with target label references doesn't
create additional fragments if the label can been resolved
locally. Target path references are not resolved locally and will
generate a fragment.
Previously the dts below would generate two fragments:
/dts-v1/;
/plugin/;
&x { a: a@0 {};};
&a { b {}; };
This commit essentially reverts part of the commit "Correct overlay
syntactic sugar for generating target-path fragments". The main reason
we want to do this is that it breaks consumers of dtbo:s that can't
resolve references between fragments in the same dtbo (like the linux
4.1 kernel). In addition creating a fragment for each label reference
substantially increases the size of the resulting dtbo for some use
cases.
Signed-off-by: Fredrik Markstrom <fredrik.markstrom@gmail.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Path references are also a string, so add TYPE_STRING marker in addition
to REF_PATH.
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
The current code throws away all the data type and grouping information
when parsing the DTS source file, which makes it difficult to
reconstruct the data format when emitting a format that can express data
types (ie. dts and yaml). Use the marker structure to mark the beginning
of each integer array block (<> and []), and the datatype contained in
each (8, 16, 32 & 64 bit widths).
Signed-off-by: Grant Likely <grant.likely@arm.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
[robh: s/MARKER_/TYPE_/]
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
A number of platforms have a need to reduce the number of DT nodes,
mostly because of two similar constraints: the size of the DT blob, and
the time it takes to parse it.
As the DT is used in more and more SoCs, and by more projects, some
constraints start to appear in bootloaders running from SRAM with an
order of magnitude of 10kB. A typical DT is in the same order of
magnitude, so any effort to reduce the blob size is welcome in such an
environment.
Some platforms also want to reach very fast boot time, and the time it
takes to parse a typical DT starts to be noticeable.
Both of these issues can be mitigated by reducing the number of nodes in
the DT. The biggest provider of nodes is usually the pin controller and
its subnodes, usually one for each valid pin configuration in a given
SoC.
Obviously, a single, fixed, set of these nodes will be used by a given
board, so we can introduce a node property that will tell the DT
compiler to drop the nodes when they are not referenced in the tree, and
as such wouldn't be useful in the targetted system.
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
We've recently added "syntactic sugar" support to generate runtime dtb
overlays using similar syntax to the compile time overlays we've had for
a while. This worked with the &label { ... } syntax, adjusting an existing
labelled node, but would fail with the &{/path} { ... } syntax attempting
to adjust an existing node referenced by its path.
The previous code would always try to use the "target" property in the
output overlay, which needs to be fixed up, and __fixups__ can only encode
symbols, not paths, so the result could never work properly.
This adds support for the &{/path} syntax for overlays, translating it into
the "target-path" encoding in the output. It also changes existing
behaviour a little because we now unconditionally one fragment for each
overlay section in the source. Previously we would only create a fragment
if we couldn't locally resolve the node referenced. We need this for
path references, because the path is supposed to be referencing something
in the (not yet known) base tree, rather than the overlay tree we are
working with now. In particular one useful case for path based overlays
is using &{/} - but the constructed overlay tree will always have a root
node, meaning that without the change that would attempt to resolve the
fragment locally, which is not what we want.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Commit 737b2df3, "overlay: Add syntactic sugar version of overlays"
introduced an empty rule for "devicetree" that created ambiguities in
the grammar and causes the following warning:
BISON dtc-parser.tab.c
dtc-parser.y: warning: 3 shift/reduce conflicts [-Wconflicts-sr]
Fix the grammar by explicitly testing for the condition the
new overlay grammar wants to use. This means duplicating a very small
amount of grammar processing code, but the alternative seems to be a
more invasive reorganization of the devicetree rule. Better to fix it
this way now and save the reorg for a separate patch.
Signed-off-by: Grant Likely <grant.likely@arm.com>
Cc: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
Cc: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
For simple overlays that use a single target there exists a
simpler syntax version.
&foo { }; generates an overlay with a single target at foo.
Signed-off-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
If we have a construct like this:
label: &handle {
...
};
Running dtc on it will cause a segfault, because we use 'target'
when it could be NULL. Move the add_label() call into the if
statement to fix this potentially bad use of a NULL pointer.
Signed-off-by: Stephen Boyd <stephen.boyd@linaro.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
struct boot_info is named that for historical reasons, and isn't
particularly meaningful. Essentially it contains all the information -
in "live" form from a single dts or dtb file. As we move towards support
for dynamic dt overlays, that name will become increasingly bad.
So, in preparation, rename it to dt_info. At the same time rename the
'the_boot_info' global to 'parser_output' since that's its actual purpose.
Unfortunately we do need the global unless we switch to bison's re-entrant
parser extensions, which would introduce its own complications.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
First remove the non-terminal name 'versioninfo' - /plugin/ doesn't really
indicate a "version" per se, and version could be confused with the dtb
output version.
Second allow the /dts-v1/; /plugin/; sequence to be repeated, for easier
use of include files - but ensure that all copies match, so you can't
include a file declaring /plugin/ in one that doesn't, or vice versa.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
This patch enable the generation of symbols & local fixup information
for trees compiled with the -@ (--symbols) option.
Using this patch labels in the tree and their users emit information
in __symbols__ and __local_fixups__ nodes.
The __fixups__ node make possible the dynamic resolution of phandle
references which are present in the plugin tree but lie in the
tree that are applying the overlay against.
Signed-off-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Jan Luebbe <jlu@pengutronix.de>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
This patch allows dtc to accept multiple /dts-v1/ tags (provided they're
all at the beginning of the input), rather than giving a syntax error.
This makes it more convenient to include one .dts file from another without
having to be careful that the /dts-v1/ tag is in exactly one of them.
We a couple of existing testcases to take advantage of this, which
simplifies them slightly.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
1937095 "Prevent crash on division by zero" fixed a crash when attempting
a division by zero using the / operator in a dts. However, it missed the
precisely equivalent crash with the % (modulus) operator. This patch fixes
the oversight.
Reported-by: Anton Blanchard <anton@samba.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Currently, attempting to divide by zero in an integer expression in a dts
file will cause dtc to crash with a division by zero (SIGFPE).
This patch corrects this to properly detect this case and raise an error.
Reported-by: Anton Blanchard <anton@samba.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
This patch changes the dtc grammar to allow following syntax
i2cexp: &i2c2 {
...
};
Current device tree compiler allows to define multiple labels when defining
the device node the first time. Typically device nodes are defined in
DTSI files. Now these nodes can be overwritten for updating some of the
properties. Typically, device nodes are overridden in DTS files.
When working with adapter boards, most of the time adapter board can fit to
multiple base boards. But depending on which base board it is connected to,
the devices on the adapter board would be children of different devices.
e.g. On dra7-evm.dts, i2c2 is exported for expansion connector whereas
on dra72-evm.dts, i2c5 is exported for expansion connector.
This causes a problem when writing a generic device tree file for
the adapter board. Because, you cannot know whether all the devices on
adapter board are present on i2c or i2c5.
The problem can be solved by adding a common label (e.g. i2cexp) in both
of the DTS files when overriding the device nodes for i2c2 or i2c5.
This way, generic adapter board file would override the i2cexp. And
depending on which base board you use the adapter board, all the devices
are automatically added for correct device nodes.
Signed-off-by: Nikhil Devshatwar <nikhil.nd@ti.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Generally edit parser error messages for brevity and clarity. Replace
the print_error() function with a a new macro for brevity and clarity in
the source.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
The print_error() function used in several places in the parser uses the
location information in yylloc to describe the location of the error.
This is not correct in most cases. yylloc gives the location of the
lookahead token, whereas the error is generally associated with one of
the already parsed non-terminals.
This patch corrects this, adding a location parameter to print_error() and
supplying it with the appropriate bison @N symbols.
This probably breaks yacc compatiblity, but too bad - accurate error
messages are more important.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Failing to open an input file, with /include/ or /incbin/ is treated as
immediately fatal inside srcfile_relative_open(). However, filing to
seek() to the requested offset in an /incbin/ is not. This is a bit oddly
inconsistent, and leaves us with a strange case that's awkward to deal with
down the line.
So, get rid of it and have failed seeks on an /incbin/ be immediately
fatal.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
To match the processing of integer literals, character literals are passed
as a string from lexer to parser then interpreted there. This is just as
awkward as it was for integer literals, without the excuse that we used to
need the information about the dts version to process them correctly.
So, move character literal processing back to the lexer as well, cleaning
things up.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
At the moment integer literals are passed from the lexer to the parser as
a string, where it's evaluated into an integer by eval_literal(). That
strange approach happened because we needed to know whether we were
processing dts-v0 or dts-v1 - only known at the parser level - to know
how to interpret the literal properly.
dts-v0 support has been gone for some time now, and the base and bits
parameters to eval_literal() are essentially useless.
So, clean things up by moving the literal interpretation back to the lexer.
This also introduces a new lexical_error() function to report malformed
literals and set the treesource_error flag so that they'll cause a parse
failure at the top level.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Allow them to take a prefix argument giving the general type of error,
which will be useful in future.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
We already use the C99 bool type from stdbool.h in a few places. However
there are many other places we represent boolean values as plain ints.
This patch changes that.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
dtc currently allows the contents of properties to be changed, and the
contents of nodes to be added to. There are situations where removing
properties or nodes may be useful. This change implements the following
syntax to do that:
/ {
/delete-property/ propname;
/delete-node/ nodename;
};
or:
/delete-node/ &noderef;
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-by: David Gibson <david@gibson.dropbear.id.au>
Written by David Gibson <david@gibson.dropbear.id.au>. Additions by me:
* Ported to ToT dtc.
* Renamed cell to integer throughout.
* Implemented value range checks.
* Allow U/L/UL/LL/ULL suffix on literals.
* Enabled the commented test.
Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>
Elements of size 8, 16, 32, and 64 bits are supported. The new
/bits/ syntax was selected so as to not pollute the reserved
keyword space with uint8/uint16/... type names.
With this patch the following property assignment:
property = /bits/ 16 <0x1234 0x5678 0x0 0xffff>;
is equivalent to:
property = <0x12345678 0x0000ffff>;
It is now also possible to directly specify a 64 bit literal in a
cell list, also known as an array using:
property = /bits/ 64 <0xdeadbeef00000000>;
It is an error to attempt to store a literal into an element that is
too small to hold the literal, and the compiler will generate an
error when it detects this. For instance:
property = /bits/ 8 <256>;
Will fail to compile. It is also an error to attempt to place a
reference in a non 32-bit element.
The documentation has been changed to reflect that the cell list
is now an array of elements that can be of sizes other than the
default 32-bit cell size.
The sized_cells test tests the creation and access of 8, 16, 32,
and 64-bit sized elements. It also tests that the creation of two
properties, one with 16 bit elements and one with 32 bit elements
result in the same property contents.
Signed-off-by: Anton Staaf <robotboy@chromium.org>
Acked-by: David Gibson <david@gibson.dropbear.id.au>
With this patch the following property assignment:
property = <0x12345678 'a' '\r' 100>;
is equivalent to:
property = <0x12345678 0x00000061 0x0000000D 0x00000064>
Signed-off-by: Anton Staaf <robotboy@chromium.org>
Acked-by: David Gibson <david@gibson.dropbear.id.au>
When nodes are modified by merging device trees, nodes to be updated/merged can
be specified by a label. Specifying nodes by full path (instead of label)
doesn't quite work. This patch fixes that.
Signed-off-by: John Bonesio <bones@secretlab.ca>
Acked-by: David Gibson <david@gibson.dropbear.id.au>
yyerror is meant to be called by the parser internal code, and it's interface
is limited. Instead create and call a new error message routine that allows
formatted strings to be used.
yyerror uses the new routine so error formatting remains consistent.
Signed-of-by: John Bonesio <bones@secretlab.ca>
Acked-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
This patch allows the following construct:
/ {
property-a = "old";
property-b = "does not change";
};
/ {
property-a = "changed";
property-c = "new";
node-a {
};
};
Where the later device tree overrides the properties found in the
earlier tree. This is useful for laying down a template device tree
in an include file and modifying it for a specific board without having
to clone the entire tree.
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
At present, both the grammar and our internal data structures mean
that there can be only one label on a node or property. This is a
fairly arbitrary constraint, given that any number of value labels can
appear at the same point, and that in C you can have any number of
labels on the same statement.
This is pretty much a non-issue now, but it may become important with
some of the extensions that Grant and I have in mind. It's not that
hard to change, so this patch does so, allowing an arbitrary number of
labels on any given node or property. As usual a testcase is added
too.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Currently, when in -Idts -Odtb or -Ifs -Odtb modes, dtc always
defaults to using 0 as the value for the boot_cpuid_phys header field.
That's correct quite often, but there are some systems where there is
no CPU with hardware ID of 0, or where we don't want to use the CPU
with hardware ID 0 at all (e.g. for AMP-style partitioning). The only
way to override this default currently, is with the -b command line
option.
This patch improves dtc to instead base the default boot_cpuid_phys
value on the reg property of the first listed subnode of /cpus. This
means that dtc will get boot_cpuid_phys correct by default in a
greater proportion of cases (since the boot cpu is usually listed
first, and this way at least the boot_cpuid_phys default will match
some existing cpu node). If the node doesn't exist or has an invalid
'reg' property (missing or not 4 bytes in length), then
boot_cpuid_phys is set to 0.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
This mod allows successful build of dtc using both bison/flex and yacc/lex.
Signed-off-by: Lukasz Wojcik <zbr@semihalf.com>
Acked-by: David Gibson <david@gibson.dropbear.id.au>
This patch cleans up our handling of input files, particularly dts
source files, but also (to an extent) other input files such as those
used by /incbin/ and those used in -I dtb and -I fs modes.
We eliminate the current clunky mechanism which combines search paths
(which we don't actually use at present) with the open relative to
current source file behaviour, which we do.
Instead there's a single srcfile_relative_open() entry point for
callers which opens a new input file relative to the current source
file (which the srcpos code tracks internally). It doesn't currently
do search paths, but we can add that later without messing with the
callers, by drawing the search path from a global (which makes sense
anyway, rather than shuffling it around the rest of the processing
code).
That suffices for non-dts input files. For the actual dts files,
srcfile_push() and srcfile_pop() wrappers open the file while also
keeping track of it as the current source file for future opens.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
yylloc is the correct way to get token positioning information.
yyloc is a bison internal variable that only works by accident.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Now that all in-kernel-tree DTS files are properly /dts-v1/,
remove direct support for the older, un-numbered DTS
source file format.
Convert existing tests to /dts-v1/ and remove support
for the conversion tests themselves.
For now, though, the conversion tool still exists.
Signed-off-by: Jon Loeliger <jdl@freescale.com>
Implemented some print and copy routines.
Made empty srcpos objects that will be used later.
Protected .h file from multiple #include's.
Added srcpos_error() and srcpos_warn().
Signed-off-by: Jon Loeliger <jdl@freescale.com>
Currently, dtc defines Linux-like names for various fixed-size integer
types. There's no good reason to do this; even Linux itself doesn't
use these names for externally visible things any more. This patch
replaces these with the C99 standardized type names from stdint.h.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
On Wed, Jun 04, 2008 at 09:26:23AM -0500, Jon Loeliger wrote:
> David Gibson wrote:
>
>> But as I said that can be dealt with in the future without breaking
>> compatibility. Objection withdrawn.
>>
>
> And on that note, I officially implore Scott to
> re-submit his binary include patch!
Scott's original patch does still have some implementation details I
didn't like. So in the interests of saving time, I've addressed some
of those, added a testcase, and and now resubmitting my revised
version of Scott's patch.
dtc: Add support for binary includes.
A property's data can be populated with a file's contents
as follows:
node {
prop = /incbin/("path/to/data");
};
A subset of a file can be included by passing start and size parameters.
For example, to include bytes 8 through 23:
node {
prop = /incbin/("path/to/data", 8, 16);
};
As with /include/, non-absolute paths are looked for in the directory
of the source file that includes them.
Implementation revised, and a testcase added by David Gibson
Signed-off-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Acked-by: Scott Wood <scottwood@freescale.com>
Currently, dtc will put the nonsense value 0xfeedbeef into the
boot_cpuid_phys field of an output blob, unless explicitly given
another value with the -b command line option. As well as being a
totally unuseful default value, this also means that dtc won't
properly preserve the boot_cpuid_phys field in -I dtb -O dtb mode.
This patch reworks things to improve the boot_cpuid handling. The new
semantics are that the output's boot_cpuid_phys value is:
the value given on the command line if -b is used
otherwise
the value from the input, if in -I dtb mode
otherwise
0
Implementation-wise we do the following:
- boot_cpuid_phys is added to struct boot_info, so that
structure now contains all of the blob's semantic information.
- dt_to_blob() and dt_to_asm() output the cpuid given in
boot_info
- dt_from_blob() fills in boot_info based on the input blob
- The other dt_from_*() functions just record 0, but we can
change this easily if e.g. we invent a way of specifying the boot cpu
in the source format.
- main() overrides the cpuid in the boot_info between input
and output if -b is given
We add some testcases to check this new behaviour.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
