coreboot-kgpe-d16/payloads/libpayload
Hung-Te Lin d04b388381 libpayload: cbgfx: Support buffered I/O
For payloads with UI based on CBGFX, they usually start by calling
clear_canvas or clear_screen and then draw the UI elements. However,
that makes the screen flicker.

A typical solution is to identify and minimize the area to redraw.
However for payloads with complicated UI and do not care about latency,
an alternative is to enable buffered I/O.

The new enable_graphics_buffer() will redirect all graphics I/O
into an invisible working buffer. To flush (redraw) the buffer to the
real screen, call flush_graphics_buffer(). To stop buffering, call
disable_graphics_buffer().

BUG=None
TEST=Add the enable, flush and disable calls to payload 'depthcharge',
     built a firmware and boots into Chrome OS recover UI. No more
     flickering. The average rendering time on x86 platform is 1.2ms.

Change-Id: Id60a2824fd9e164feae16b92b68b003beabea8d3
Signed-off-by: Hung-Te Lin <hungte@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/44654
Reviewed-by: Julius Werner <jwerner@chromium.org>
Reviewed-by: Yu-Ping Wu <yupingso@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
2020-08-28 21:40:58 +00:00
..
arch libpayload: Cache physical location of CBMEM entries 2020-08-24 09:13:30 +00:00
bin treewide: Remove "this file is part of" lines 2020-05-11 17:11:40 +00:00
configs libpayload/defconfig: Set default heap size to 1MiB 2020-08-17 06:10:49 +00:00
crypto treewide: Remove "this file is part of" lines 2020-05-11 17:11:40 +00:00
curses payloads/libpayload/curses/menu/eti.h: Remove unneeded whitespaces 2020-07-25 01:25:16 +00:00
drivers libpayload: cbgfx: Support buffered I/O 2020-08-28 21:40:58 +00:00
gdb libpayload: gdb: Condition video console init on LP_VIDEO_CONSOLE 2020-06-22 12:24:42 +00:00
include libpayload: cbgfx: Support buffered I/O 2020-08-28 21:40:58 +00:00
libc libpayload: memmove: Don't make expectations of architecture memcpy 2020-08-24 09:24:06 +00:00
libcbfs treewide: Remove "this file is part of" lines 2020-05-11 17:11:40 +00:00
liblz4 lz4: Fix out-of-bounds reads 2020-03-02 15:03:03 +00:00
liblzma treewide: Remove "this file is part of" lines 2020-05-11 17:11:40 +00:00
libpci treewide: Remove "this file is part of" lines 2020-05-11 17:11:40 +00:00
sample treewide: Remove "this file is part of" lines 2020-05-11 17:11:40 +00:00
tests
Doxyfile
Kconfig libpayload: cbgfx: Replace bilinear resampling with Lanczos 2020-07-09 00:32:17 +00:00
LICENSES
LICENSE_GPL
Makefile treewide: Remove "this file is part of" lines 2020-05-11 17:11:40 +00:00
Makefile.inc treewide: Remove "this file is part of" lines 2020-05-11 17:11:40 +00:00
README payloads/libpayload: Update a Makefile for sample libpayload 2019-06-21 09:16:36 +00:00

README

-------------------------------------------------------------------------------
libpayload README
-------------------------------------------------------------------------------

libpayload is a minimal library to support standalone payloads
that can be booted with firmware like coreboot. It handles the setup
code, and provides common C library symbols such as malloc() and printf().

Note: This is _not_ a standard library for use with an operating system,
rather it's only useful for coreboot payload development!
See https://www.coreboot.org for details on coreboot.


Installation
------------

 $ git clone https://review.coreboot.org/coreboot.git

 $ cd coreboot/payloads/libpayload

 $ make menuconfig

 $ make

 $ make install (optional, will install into ./install per default)

On x86 systems, libpayload will always be 32-bit even if your host OS runs
in 64-bit, so you might have to install the 32-bit libgcc version.
On Debian systems you'd do 'apt-get install gcc-multilib' for example.

Run 'make distclean' before switching boards. This command will remove
your current .config file, so you need 'make menuconfig' again or
'make defconfig' in order to set up configuration. Default configuration
is based on 'configs/defconfig'. See the configs/ directory for examples
of configuration.


Usage
-----

Here's an example of a very simple payload (hello.c) and how to build it:

 #include <libpayload.h>

 int main(void)
 {
     printf("Hello, world!\n");
     return 0;
 }

Building the payload using the 'lpgcc' compiler wrapper:

 $ lpgcc -o hello.elf hello.c

Please see the sample/ directory for details.


Website and Mailing List
------------------------

The main website is https://www.coreboot.org/Libpayload.

For additional information, patches, and discussions, please join the
coreboot mailing list at https://www.coreboot.org/Mailinglist, where most
libpayload developers are subscribed.


Copyright and License
---------------------

See LICENSES.