[U-Boot] [PATCH 0/6] Adjust command macros to allow smaller U-Boot size

[Simon Glass]

A large chunk of U-Boot's executable size is the code to process and
execute commands. This is reasonable, since commands and scripts are
an important part of U-Boot's feature set and provide much of its
flexibility.

However, for some applications only a very limited set of commands is
required. Where image size is important, it is desirable to be able to
easily remove unwanted code.

This series introduces a new board_run_command() function which can
be used to run a small subset of commands as required by the board
(typically load and bootm), thus allowing the rest of the commands
to be automatically and reliably dropped from the image using toolchain
dead code elimination.

Tests on snow (ARMv7) show this reduces image size dramatically, more
than just undefining all the commands:

   text	   data	    bss	    dec	    hex	filename
before:
 356359	  12550	 300056	 668965	  a3525	b/snow/u-boot
with all commands undefined:
 155336	   5402	   8624	 169362	  29592	b/snow/u-boot
with this series:
 123177	   2958	   1544	 127679	  1f2bf	b/snow/u-boot

The difference is more pronounced the more effort is put into reducing
the image size. For example, removing additional subsystem options yields:

   text	   data	    bss	    dec	    hex	filename
with all commands undefined and most subsystems:
  86479	   4186	   7480	  98145	  17f61	b/snow/u-boot
with this series:
  52395	   1818	    228	  54441	   d4a9	b/snow/u-boot

Further, it is possible to enable some of the split-use options like
CONFIG_CMD_USB, and get USB support without the unwanted command
overhead (it would be better if USB had a separate option for the command
and the USB stack, but that is not the case, and a few other features have
a similar problem).

U-Boot can then become a really minimal boot loader, with only the required
functions available. Simply undefining various unwanted commands in the
board config is not as effective, and is much more time-consuming to
figure out. Apart from the cost of the parsing code, the commands
necessarily provide a lot options and features which are not required
by many boards.

In particular, with this series, it is possible to run a minimal U-Boot
within the SRAM of a modern SoC, providing the benefits of the full U-Boot
environment with the small size of SPL. This helps to bridge the gap
somewhat. A key difference between U-Boot and SPL is the inclusion of the
command parser, and this small size of SPL is a key reason why some boards
currently use 'falcon mode', where only SPL is used to boot a kernel.

This series has a fairly small impact on the source code, changing
command.h and a fairly small change to each list of subcommands (there
are about 19 such sites in U-Boot).

Note: some effort was expended in trying to obtain the same result with
just linker code elimination. However this did not work, since the linker
would not eliminate some transitively-called functions like do_fdt() even
when callers are removed.


Simon Glass (6):
  Add an info word to commands
  Refactor command macros so they can compile to nothing
  Add CONFIG_CMDLINE to allow removal of all commands
  main: Exclude getline code when CONFIG_CMDLINE is not defined
  main: Process FDT options even without CONFIG_BOOTDELAY
  sandbox: Add board_run_command() function

 README                                 |   8 +++
 arch/x86/cpu/u-boot.lds                |   4 ++
 board/inka4x0/inkadiag.c               |  12 ++--
 board/intercontrol/digsy_mtc/cmd_mtc.c |  20 +++----
 board/sandbox/sandbox/sandbox.c        |  10 ++++
 common/cmd_bmp.c                       |   8 +--
 common/cmd_bootm.c                     |  39 ++++++++-----
 common/cmd_bootstage.c                 |  10 ++--
 common/cmd_cbfs.c                      |   3 +-
 common/cmd_clk.c                       |   6 +-
 common/cmd_demo.c                      |  10 ++--
 common/cmd_help.c                      |   4 ++
 common/cmd_i2c.c                       |  34 +++++------
 common/cmd_nvedit.c                    |  42 +++++++-------
 common/cmd_onenand.c                   |  23 ++++----
 common/cmd_pxe.c                       |   6 +-
 common/cmd_sandbox.c                   |  14 ++---
 common/cmd_sound.c                     |   8 +--
 common/cmd_spl.c                       |  14 ++---
 common/cmd_tpm.c                       |  52 ++++++++---------
 common/command.c                       |  12 +++-
 common/main.c                          | 101 ++++++++++++++++++++++----------
 drivers/gpio/pca953x.c                 |  14 ++---
 drivers/gpio/tca642x.c                 |  14 ++---
 drivers/misc/ds4510.c                  |  24 ++++----
 include/command.h                      | 102 ++++++++++++++++++++++++++++-----
 include/config_defaults.h              |   2 +
 include/config_fallbacks.h             |   7 +++
 test/dm/cmd_dm.c                       |  10 ++--
 29 files changed, 392 insertions(+), 221 deletions(-)

-- 
1.9.1.423.g4596e3a