xref: /openbmc/u-boot/tools/binman/README (revision b3820ba9)
1# SPDX-License-Identifier: GPL-2.0+
2# Copyright (c) 2016 Google, Inc
3
4Introduction
5------------
6
7Firmware often consists of several components which must be packaged together.
8For example, we may have SPL, U-Boot, a device tree and an environment area
9grouped together and placed in MMC flash. When the system starts, it must be
10able to find these pieces.
11
12So far U-Boot has not provided a way to handle creating such images in a
13general way. Each SoC does what it needs to build an image, often packing or
14concatenating images in the U-Boot build system.
15
16Binman aims to provide a mechanism for building images, from simple
17SPL + U-Boot combinations, to more complex arrangements with many parts.
18
19
20What it does
21------------
22
23Binman reads your board's device tree and finds a node which describes the
24required image layout. It uses this to work out what to place where. The
25output file normally contains the device tree, so it is in principle possible
26to read an image and extract its constituent parts.
27
28
29Features
30--------
31
32So far binman is pretty simple. It supports binary blobs, such as 'u-boot',
33'spl' and 'fdt'. It supports empty entries (such as setting to 0xff). It can
34place entries at a fixed location in the image, or fit them together with
35suitable padding and alignment. It provides a way to process binaries before
36they are included, by adding a Python plug-in. The device tree is available
37to U-Boot at run-time so that the images can be interpreted.
38
39Binman does not yet update the device tree with the final location of
40everything when it is done. A simple C structure could be generated for
41constrained environments like SPL (using dtoc) but this is also not
42implemented.
43
44Binman can also support incorporating filesystems in the image if required.
45For example x86 platforms may use CBFS in some cases.
46
47Binman is intended for use with U-Boot but is designed to be general enough
48to be useful in other image-packaging situations.
49
50
51Motivation
52----------
53
54Packaging of firmware is quite a different task from building the various
55parts. In many cases the various binaries which go into the image come from
56separate build systems. For example, ARM Trusted Firmware is used on ARMv8
57devices but is not built in the U-Boot tree. If a Linux kernel is included
58in the firmware image, it is built elsewhere.
59
60It is of course possible to add more and more build rules to the U-Boot
61build system to cover these cases. It can shell out to other Makefiles and
62build scripts. But it seems better to create a clear divide between building
63software and packaging it.
64
65At present this is handled by manual instructions, different for each board,
66on how to create images that will boot. By turning these instructions into a
67standard format, we can support making valid images for any board without
68manual effort, lots of READMEs, etc.
69
70Benefits:
71- Each binary can have its own build system and tool chain without creating
72any dependencies between them
73- Avoids the need for a single-shot build: individual parts can be updated
74and brought in as needed
75- Provides for a standard image description available in the build and at
76run-time
77- SoC-specific image-signing tools can be accomodated
78- Avoids cluttering the U-Boot build system with image-building code
79- The image description is automatically available at run-time in U-Boot,
80SPL. It can be made available to other software also
81- The image description is easily readable (it's a text file in device-tree
82format) and permits flexible packing of binaries
83
84
85Terminology
86-----------
87
88Binman uses the following terms:
89
90- image - an output file containing a firmware image
91- binary - an input binary that goes into the image
92
93
94Relationship to FIT
95-------------------
96
97FIT is U-Boot's official image format. It supports multiple binaries with
98load / execution addresses, compression. It also supports verification
99through hashing and RSA signatures.
100
101FIT was originally designed to support booting a Linux kernel (with an
102optional ramdisk) and device tree chosen from various options in the FIT.
103Now that U-Boot supports configuration via device tree, it is possible to
104load U-Boot from a FIT, with the device tree chosen by SPL.
105
106Binman considers FIT to be one of the binaries it can place in the image.
107
108Where possible it is best to put as much as possible in the FIT, with binman
109used to deal with cases not covered by FIT. Examples include initial
110execution (since FIT itself does not have an executable header) and dealing
111with device boundaries, such as the read-only/read-write separation in SPI
112flash.
113
114For U-Boot, binman should not be used to create ad-hoc images in place of
115FIT.
116
117
118Relationship to mkimage
119-----------------------
120
121The mkimage tool provides a means to create a FIT. Traditionally it has
122needed an image description file: a device tree, like binman, but in a
123different format. More recently it has started to support a '-f auto' mode
124which can generate that automatically.
125
126More relevant to binman, mkimage also permits creation of many SoC-specific
127image types. These can be listed by running 'mkimage -T list'. Examples
128include 'rksd', the Rockchip SD/MMC boot format. The mkimage tool is often
129called from the U-Boot build system for this reason.
130
131Binman considers the output files created by mkimage to be binary blobs
132which it can place in an image. Binman does not replace the mkimage tool or
133this purpose. It would be possible in some situations to create a new entry
134type for the images in mkimage, but this would not add functionality. It
135seems better to use the mkimage tool to generate binaries and avoid blurring
136the boundaries between building input files (mkimage) and packaging then
137into a final image (binman).
138
139
140Example use of binman in U-Boot
141-------------------------------
142
143Binman aims to replace some of the ad-hoc image creation in the U-Boot
144build system.
145
146Consider sunxi. It has the following steps:
147
1481. It uses a custom mksunxiboot tool to build an SPL image called
149sunxi-spl.bin. This should probably move into mkimage.
150
1512. It uses mkimage to package U-Boot into a legacy image file (so that it can
152hold the load and execution address) called u-boot.img.
153
1543. It builds a final output image called u-boot-sunxi-with-spl.bin which
155consists of sunxi-spl.bin, some padding and u-boot.img.
156
157Binman is intended to replace the last step. The U-Boot build system builds
158u-boot.bin and sunxi-spl.bin. Binman can then take over creation of
159sunxi-spl.bin (by calling mksunxiboot, or hopefully one day mkimage). In any
160case, it would then create the image from the component parts.
161
162This simplifies the U-Boot Makefile somewhat, since various pieces of logic
163can be replaced by a call to binman.
164
165
166Example use of binman for x86
167-----------------------------
168
169In most cases x86 images have a lot of binary blobs, 'black-box' code
170provided by Intel which must be run for the platform to work. Typically
171these blobs are not relocatable and must be placed at fixed areas in the
172firmware image.
173
174Currently this is handled by ifdtool, which places microcode, FSP, MRC, VGA
175BIOS, reference code and Intel ME binaries into a u-boot.rom file.
176
177Binman is intended to replace all of this, with ifdtool left to handle only
178the configuration of the Intel-format descriptor.
179
180
181Running binman
182--------------
183
184Type:
185
186	binman -b <board_name>
187
188to build an image for a board. The board name is the same name used when
189configuring U-Boot (e.g. for sandbox_defconfig the board name is 'sandbox').
190Binman assumes that the input files for the build are in ../b/<board_name>.
191
192Or you can specify this explicitly:
193
194	binman -I <build_path>
195
196where <build_path> is the build directory containing the output of the U-Boot
197build.
198
199(Future work will make this more configurable)
200
201In either case, binman picks up the device tree file (u-boot.dtb) and looks
202for its instructions in the 'binman' node.
203
204Binman has a few other options which you can see by running 'binman -h'.
205
206
207Enabling binman for a board
208---------------------------
209
210At present binman is invoked from a rule in the main Makefile. Typically you
211will have a rule like:
212
213ifneq ($(CONFIG_ARCH_<something>),)
214u-boot-<your_suffix>.bin: <input_file_1> <input_file_2> checkbinman FORCE
215	$(call if_changed,binman)
216endif
217
218This assumes that u-boot-<your_suffix>.bin is a target, and is the final file
219that you need to produce. You can make it a target by adding it to ALL-y
220either in the main Makefile or in a config.mk file in your arch subdirectory.
221
222Once binman is executed it will pick up its instructions from a device-tree
223file, typically <soc>-u-boot.dtsi, where <soc> is your CONFIG_SYS_SOC value.
224You can use other, more specific CONFIG options - see 'Automatic .dtsi
225inclusion' below.
226
227
228Image description format
229------------------------
230
231The binman node is called 'binman'. An example image description is shown
232below:
233
234	binman {
235		filename = "u-boot-sunxi-with-spl.bin";
236		pad-byte = <0xff>;
237		blob {
238			filename = "spl/sunxi-spl.bin";
239		};
240		u-boot {
241			offset = <CONFIG_SPL_PAD_TO>;
242		};
243	};
244
245
246This requests binman to create an image file called u-boot-sunxi-with-spl.bin
247consisting of a specially formatted SPL (spl/sunxi-spl.bin, built by the
248normal U-Boot Makefile), some 0xff padding, and a U-Boot legacy image. The
249padding comes from the fact that the second binary is placed at
250CONFIG_SPL_PAD_TO. If that line were omitted then the U-Boot binary would
251immediately follow the SPL binary.
252
253The binman node describes an image. The sub-nodes describe entries in the
254image. Each entry represents a region within the overall image. The name of
255the entry (blob, u-boot) tells binman what to put there. For 'blob' we must
256provide a filename. For 'u-boot', binman knows that this means 'u-boot.bin'.
257
258Entries are normally placed into the image sequentially, one after the other.
259The image size is the total size of all entries. As you can see, you can
260specify the start offset of an entry using the 'offset' property.
261
262Note that due to a device tree requirement, all entries must have a unique
263name. If you want to put the same binary in the image multiple times, you can
264use any unique name, with the 'type' property providing the type.
265
266The attributes supported for entries are described below.
267
268offset:
269	This sets the offset of an entry within the image or section containing
270	it. The first byte of the image is normally at offset 0. If 'offset' is
271	not provided, binman sets it to the end of the previous region, or the
272	start of the image's entry area (normally 0) if there is no previous
273	region.
274
275align:
276	This sets the alignment of the entry. The entry offset is adjusted
277	so that the entry starts on an aligned boundary within the image. For
278	example 'align = <16>' means that the entry will start on a 16-byte
279	boundary. Alignment shold be a power of 2. If 'align' is not
280	provided, no alignment is performed.
281
282size:
283	This sets the size of the entry. The contents will be padded out to
284	this size. If this is not provided, it will be set to the size of the
285	contents.
286
287pad-before:
288	Padding before the contents of the entry. Normally this is 0, meaning
289	that the contents start at the beginning of the entry. This can be
290	offset the entry contents a little. Defaults to 0.
291
292pad-after:
293	Padding after the contents of the entry. Normally this is 0, meaning
294	that the entry ends at the last byte of content (unless adjusted by
295	other properties). This allows room to be created in the image for
296	this entry to expand later. Defaults to 0.
297
298align-size:
299	This sets the alignment of the entry size. For example, to ensure
300	that the size of an entry is a multiple of 64 bytes, set this to 64.
301	If 'align-size' is not provided, no alignment is performed.
302
303align-end:
304	This sets the alignment of the end of an entry. Some entries require
305	that they end on an alignment boundary, regardless of where they
306	start. This does not move the start of the entry, so the contents of
307	the entry will still start at the beginning. But there may be padding
308	at the end. If 'align-end' is not provided, no alignment is performed.
309
310filename:
311	For 'blob' types this provides the filename containing the binary to
312	put into the entry. If binman knows about the entry type (like
313	u-boot-bin), then there is no need to specify this.
314
315type:
316	Sets the type of an entry. This defaults to the entry name, but it is
317	possible to use any name, and then add (for example) 'type = "u-boot"'
318	to specify the type.
319
320offset-unset:
321	Indicates that the offset of this entry should not be set by placing
322	it immediately after the entry before. Instead, is set by another
323	entry which knows where this entry should go. When this boolean
324	property is present, binman will give an error if another entry does
325	not set the offset (with the GetOffsets() method).
326
327image-pos:
328	This cannot be set on entry (or at least it is ignored if it is), but
329	with the -u option, binman will set it to the absolute image position
330	for each entry. This makes it easy to find out exactly where the entry
331	ended up in the image, regardless of parent sections, etc.
332
333expand-size:
334	Expand the size of this entry to fit available space. This space is only
335	limited by the size of the image/section and the position of the next
336	entry.
337
338The attributes supported for images and sections are described below. Several
339are similar to those for entries.
340
341size:
342	Sets the image size in bytes, for example 'size = <0x100000>' for a
343	1MB image.
344
345align-size:
346	This sets the alignment of the image size. For example, to ensure
347	that the image ends on a 512-byte boundary, use 'align-size = <512>'.
348	If 'align-size' is not provided, no alignment is performed.
349
350pad-before:
351	This sets the padding before the image entries. The first entry will
352	be positioned after the padding. This defaults to 0.
353
354pad-after:
355	This sets the padding after the image entries. The padding will be
356	placed after the last entry. This defaults to 0.
357
358pad-byte:
359	This specifies the pad byte to use when padding in the image. It
360	defaults to 0. To use 0xff, you would add 'pad-byte = <0xff>'.
361
362filename:
363	This specifies the image filename. It defaults to 'image.bin'.
364
365sort-by-offset:
366	This causes binman to reorder the entries as needed to make sure they
367	are in increasing positional order. This can be used when your entry
368	order may not match the positional order. A common situation is where
369	the 'offset' properties are set by CONFIG options, so their ordering is
370	not known a priori.
371
372	This is a boolean property so needs no value. To enable it, add a
373	line 'sort-by-offset;' to your description.
374
375multiple-images:
376	Normally only a single image is generated. To create more than one
377	image, put this property in the binman node. For example, this will
378	create image1.bin containing u-boot.bin, and image2.bin containing
379	both spl/u-boot-spl.bin and u-boot.bin:
380
381	binman {
382		multiple-images;
383		image1 {
384			u-boot {
385			};
386		};
387
388		image2 {
389			spl {
390			};
391			u-boot {
392			};
393		};
394	};
395
396end-at-4gb:
397	For x86 machines the ROM offsets start just before 4GB and extend
398	up so that the image finished at the 4GB boundary. This boolean
399	option can be enabled to support this. The image size must be
400	provided so that binman knows when the image should start. For an
401	8MB ROM, the offset of the first entry would be 0xfff80000 with
402	this option, instead of 0 without this option.
403
404skip-at-start:
405	This property specifies the entry offset of the first entry.
406
407	For PowerPC mpc85xx based CPU, CONFIG_SYS_TEXT_BASE is the entry
408	offset of the first entry. It can be 0xeff40000 or 0xfff40000 for
409	nor flash boot, 0x201000 for sd boot etc.
410
411	'end-at-4gb' property is not applicable where CONFIG_SYS_TEXT_BASE +
412	Image size != 4gb.
413
414Examples of the above options can be found in the tests. See the
415tools/binman/test directory.
416
417It is possible to have the same binary appear multiple times in the image,
418either by using a unit number suffix (u-boot@0, u-boot@1) or by using a
419different name for each and specifying the type with the 'type' attribute.
420
421
422Sections and hierachical images
423-------------------------------
424
425Sometimes it is convenient to split an image into several pieces, each of which
426contains its own set of binaries. An example is a flash device where part of
427the image is read-only and part is read-write. We can set up sections for each
428of these, and place binaries in them independently. The image is still produced
429as a single output file.
430
431This feature provides a way of creating hierarchical images. For example here
432is an example image with two copies of U-Boot. One is read-only (ro), intended
433to be written only in the factory. Another is read-write (rw), so that it can be
434upgraded in the field. The sizes are fixed so that the ro/rw boundary is known
435and can be programmed:
436
437	binman {
438		section@0 {
439			read-only;
440			name-prefix = "ro-";
441			size = <0x100000>;
442			u-boot {
443			};
444		};
445		section@1 {
446			name-prefix = "rw-";
447			size = <0x100000>;
448			u-boot {
449			};
450		};
451	};
452
453This image could be placed into a SPI flash chip, with the protection boundary
454set at 1MB.
455
456A few special properties are provided for sections:
457
458read-only:
459	Indicates that this section is read-only. This has no impact on binman's
460	operation, but his property can be read at run time.
461
462name-prefix:
463	This string is prepended to all the names of the binaries in the
464	section. In the example above, the 'u-boot' binaries which actually be
465	renamed to 'ro-u-boot' and 'rw-u-boot'. This can be useful to
466	distinguish binaries with otherwise identical names.
467
468
469Entry Documentation
470-------------------
471
472For details on the various entry types supported by binman and how to use them,
473see README.entries. This is generated from the source code using:
474
475	binman -E >tools/binman/README.entries
476
477
478Hashing Entries
479---------------
480
481It is possible to ask binman to hash the contents of an entry and write that
482value back to the device-tree node. For example:
483
484	binman {
485		u-boot {
486			hash {
487				algo = "sha256";
488			};
489		};
490	};
491
492Here, a new 'value' property will be written to the 'hash' node containing
493the hash of the 'u-boot' entry. Only SHA256 is supported at present. Whole
494sections can be hased if desired, by adding the 'hash' node to the section.
495
496The has value can be chcked at runtime by hashing the data actually read and
497comparing this has to the value in the device tree.
498
499
500Order of image creation
501-----------------------
502
503Image creation proceeds in the following order, for each entry in the image.
504
5051. AddMissingProperties() - binman can add calculated values to the device
506tree as part of its processing, for example the offset and size of each
507entry. This method adds any properties associated with this, expanding the
508device tree as needed. These properties can have placeholder values which are
509set later by SetCalculatedProperties(). By that stage the size of sections
510cannot be changed (since it would cause the images to need to be repacked),
511but the correct values can be inserted.
512
5132. ProcessFdt() - process the device tree information as required by the
514particular entry. This may involve adding or deleting properties. If the
515processing is complete, this method should return True. If the processing
516cannot complete because it needs the ProcessFdt() method of another entry to
517run first, this method should return False, in which case it will be called
518again later.
519
5203. GetEntryContents() - the contents of each entry are obtained, normally by
521reading from a file. This calls the Entry.ObtainContents() to read the
522contents. The default version of Entry.ObtainContents() calls
523Entry.GetDefaultFilename() and then reads that file. So a common mechanism
524to select a file to read is to override that function in the subclass. The
525functions must return True when they have read the contents. Binman will
526retry calling the functions a few times if False is returned, allowing
527dependencies between the contents of different entries.
528
5294. GetEntryOffsets() - calls Entry.GetOffsets() for each entry. This can
530return a dict containing entries that need updating. The key should be the
531entry name and the value is a tuple (offset, size). This allows an entry to
532provide the offset and size for other entries. The default implementation
533of GetEntryOffsets() returns {}.
534
5355. PackEntries() - calls Entry.Pack() which figures out the offset and
536size of an entry. The 'current' image offset is passed in, and the function
537returns the offset immediately after the entry being packed. The default
538implementation of Pack() is usually sufficient.
539
5406. CheckSize() - checks that the contents of all the entries fits within
541the image size. If the image does not have a defined size, the size is set
542large enough to hold all the entries.
543
5447. CheckEntries() - checks that the entries do not overlap, nor extend
545outside the image.
546
5478. SetCalculatedProperties() - update any calculated properties in the device
548tree. This sets the correct 'offset' and 'size' vaues, for example.
549
5509. ProcessEntryContents() - this calls Entry.ProcessContents() on each entry.
551The default implementatoin does nothing. This can be overriden to adjust the
552contents of an entry in some way. For example, it would be possible to create
553an entry containing a hash of the contents of some other entries. At this
554stage the offset and size of entries should not be adjusted.
555
55610. WriteSymbols() - write the value of symbols into the U-Boot SPL binary.
557See 'Access to binman entry offsets at run time' below for a description of
558what happens in this stage.
559
56011. BuildImage() - builds the image and writes it to a file. This is the final
561step.
562
563
564Automatic .dtsi inclusion
565-------------------------
566
567It is sometimes inconvenient to add a 'binman' node to the .dts file for each
568board. This can be done by using #include to bring in a common file. Another
569approach supported by the U-Boot build system is to automatically include
570a common header. You can then put the binman node (and anything else that is
571specific to U-Boot, such as u-boot,dm-pre-reloc properies) in that header
572file.
573
574Binman will search for the following files in arch/<arch>/dts:
575
576   <dts>-u-boot.dtsi where <dts> is the base name of the .dts file
577   <CONFIG_SYS_SOC>-u-boot.dtsi
578   <CONFIG_SYS_CPU>-u-boot.dtsi
579   <CONFIG_SYS_VENDOR>-u-boot.dtsi
580   u-boot.dtsi
581
582U-Boot will only use the first one that it finds. If you need to include a
583more general file you can do that from the more specific file using #include.
584If you are having trouble figuring out what is going on, you can uncomment
585the 'warning' line in scripts/Makefile.lib to see what it has found:
586
587   # Uncomment for debugging
588   # This shows all the files that were considered and the one that we chose.
589   # u_boot_dtsi_options_debug = $(u_boot_dtsi_options_raw)
590
591
592Access to binman entry offsets at run time (symbols)
593----------------------------------------------------
594
595Binman assembles images and determines where each entry is placed in the image.
596This information may be useful to U-Boot at run time. For example, in SPL it
597is useful to be able to find the location of U-Boot so that it can be executed
598when SPL is finished.
599
600Binman allows you to declare symbols in the SPL image which are filled in
601with their correct values during the build. For example:
602
603    binman_sym_declare(ulong, u_boot_any, offset);
604
605declares a ulong value which will be assigned to the offset of any U-Boot
606image (u-boot.bin, u-boot.img, u-boot-nodtb.bin) that is present in the image.
607You can access this value with something like:
608
609    ulong u_boot_offset = binman_sym(ulong, u_boot_any, offset);
610
611Thus u_boot_offset will be set to the offset of U-Boot in memory, assuming that
612the whole image has been loaded, or is available in flash. You can then jump to
613that address to start U-Boot.
614
615At present this feature is only supported in SPL. In principle it is possible
616to fill in such symbols in U-Boot proper, as well.
617
618
619Access to binman entry offsets at run time (fdt)
620------------------------------------------------
621
622Binman can update the U-Boot FDT to include the final position and size of
623each entry in the images it processes. The option to enable this is -u and it
624causes binman to make sure that the 'offset', 'image-pos' and 'size' properties
625are set correctly for every entry. Since it is not necessary to specify these in
626the image definition, binman calculates the final values and writes these to
627the device tree. These can be used by U-Boot at run-time to find the location
628of each entry.
629
630
631Compression
632-----------
633
634Binman support compression for 'blob' entries (those of type 'blob' and
635derivatives). To enable this for an entry, add a 'compression' property:
636
637    blob {
638        filename = "datafile";
639        compression = "lz4";
640    };
641
642The entry will then contain the compressed data, using the 'lz4' compression
643algorithm. Currently this is the only one that is supported.
644
645
646
647Map files
648---------
649
650The -m option causes binman to output a .map file for each image that it
651generates. This shows the offset and size of each entry. For example:
652
653      Offset      Size  Name
654    00000000  00000028  main-section
655     00000000  00000010  section@0
656      00000000  00000004  u-boot
657     00000010  00000010  section@1
658      00000000  00000004  u-boot
659
660This shows a hierarchical image with two sections, each with a single entry. The
661offsets of the sections are absolute hex byte offsets within the image. The
662offsets of the entries are relative to their respective sections. The size of
663each entry is also shown, in bytes (hex). The indentation shows the entries
664nested inside their sections.
665
666
667Passing command-line arguments to entries
668-----------------------------------------
669
670Sometimes it is useful to pass binman the value of an entry property from the
671command line. For example some entries need access to files and it is not
672always convenient to put these filenames in the image definition (device tree).
673
674The-a option supports this:
675
676    -a<prop>=<value>
677
678where
679
680    <prop> is the property to set
681    <value> is the value to set it to
682
683Not all properties can be provided this way. Only some entries support it,
684typically for filenames.
685
686
687Code coverage
688-------------
689
690Binman is a critical tool and is designed to be very testable. Entry
691implementations target 100% test coverage. Run 'binman -T' to check this.
692
693To enable Python test coverage on Debian-type distributions (e.g. Ubuntu):
694
695   $ sudo apt-get install python-coverage python-pytest
696
697
698Advanced Features / Technical docs
699----------------------------------
700
701The behaviour of entries is defined by the Entry class. All other entries are
702a subclass of this. An important subclass is Entry_blob which takes binary
703data from a file and places it in the entry. In fact most entry types are
704subclasses of Entry_blob.
705
706Each entry type is a separate file in the tools/binman/etype directory. Each
707file contains a class called Entry_<type> where <type> is the entry type.
708New entry types can be supported by adding new files in that directory.
709These will automatically be detected by binman when needed.
710
711Entry properties are documented in entry.py. The entry subclasses are free
712to change the values of properties to support special behaviour. For example,
713when Entry_blob loads a file, it sets content_size to the size of the file.
714Entry classes can adjust other entries. For example, an entry that knows
715where other entries should be positioned can set up those entries' offsets
716so they don't need to be set in the binman decription. It can also adjust
717entry contents.
718
719Most of the time such essoteric behaviour is not needed, but it can be
720essential for complex images.
721
722If you need to specify a particular device-tree compiler to use, you can define
723the DTC environment variable. This can be useful when the system dtc is too
724old.
725
726To enable a full backtrace and other debugging features in binman, pass
727BINMAN_DEBUG=1 to your build:
728
729   make sandbox_defconfig
730   make BINMAN_DEBUG=1
731
732
733History / Credits
734-----------------
735
736Binman takes a lot of inspiration from a Chrome OS tool called
737'cros_bundle_firmware', which I wrote some years ago. That tool was based on
738a reasonably simple and sound design but has expanded greatly over the
739years. In particular its handling of x86 images is convoluted.
740
741Quite a few lessons have been learned which are hopefully applied here.
742
743
744Design notes
745------------
746
747On the face of it, a tool to create firmware images should be fairly simple:
748just find all the input binaries and place them at the right place in the
749image. The difficulty comes from the wide variety of input types (simple
750flat binaries containing code, packaged data with various headers), packing
751requirments (alignment, spacing, device boundaries) and other required
752features such as hierarchical images.
753
754The design challenge is to make it easy to create simple images, while
755allowing the more complex cases to be supported. For example, for most
756images we don't much care exactly where each binary ends up, so we should
757not have to specify that unnecessarily.
758
759New entry types should aim to provide simple usage where possible. If new
760core features are needed, they can be added in the Entry base class.
761
762
763To do
764-----
765
766Some ideas:
767- Use of-platdata to make the information available to code that is unable
768  to use device tree (such as a very small SPL image)
769- Allow easy building of images by specifying just the board name
770- Produce a full Python binding for libfdt (for upstream). This is nearing
771    completion but some work remains
772- Add an option to decode an image into the constituent binaries
773- Support building an image for a board (-b) more completely, with a
774  configurable build directory
775- Consider making binman work with buildman, although if it is used in the
776  Makefile, this will be automatic
777
778--
779Simon Glass <sjg@chromium.org>
7807/7/2016
781