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The current Buildroot defconfigs for Raspberry Pi and Raspberry Pi 2
instantiate a console on tty1, which appears on HDMI. Add a console on
the serial port (ttyAMA0) to be more consistent with other defconfigs
and provide a better out-of-the-box experience to users used to have a
serial console from Buildroot defconfigs.
This requires three changes:
1. have two 'console=' entries in the kernel command line: tty1,
then ttyAMA0;
2. change BR2_TARGET_GENERIC_GETTY_PORT to "console", so it starts
a getty on the last console= passed to the kernel, ttyAMA0;
3. add a new getty on tty1 to the generated inittab.
Step 2 is actually obtained by removing BR2_TARGET_GENERIC_GETTY_PORT
entirely from the defconfigs, since "console" is the default value.
Step 3 requires a post-build script since the Buildroot makefiles can
configure only one console.
Note: instead of simply adding a new getty on ttyAMA0 (which would
work) this patch actually changes BR2_TARGET_GENERIC_GETTY_PORT to
instantiate a console on UART, then adds back tty1 via
post-build.sh. This is done only to avoid the "GENERIC_SERIAL" comment
where we instantiate an HDMI console, then instantiate a really-serial
console on another line.
The result is these two inittab lines:
console::respawn:/sbin/getty -L console 0 vt100 # GENERIC_SERIAL
tty1::respawn:/sbin/getty -L tty1 0 vt100 # HDMI console
Cc: Yann E. MORIN <yann.morin.1998@free.fr>
Cc: Arnout Vandecappelle <arnout@mind.be>
Signed-off-by: Luca Ceresoli <luca@lucaceresoli.net>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Raspberry Pi
Intro
=====
These instructions apply to all models of the Raspberry Pi:
- the original models A and B,
- the "enhanced" models A+ and B+,
- the model B2 (aka Raspberry Pi 2).
How to build it
===============
Configure Buildroot
-------------------
There are two RaspberryPi defconfig files in Buildroot, one for each
major variant, which you should base your work on:
For models A, B, A+ or B+:
$ make raspberrypi_defconfig
And for model 2 B:
$ make raspberrypi2_defconfig
Build the rootfs
----------------
Note: you will need to have access to the network, since Buildroot will
download the packages' sources.
You may now build your rootfs with:
$ make
(This may take a while, consider getting yourself a coffee ;-) )
Result of the build
-------------------
After building, you should obtain this tree:
output/images/
+-- bcm2708-rpi-b.dtb [1]
+-- bcm2708-rpi-b-plus.dtb [1]
+-- bcm2709-rpi-2-b.dtb [1]
+-- boot.vfat
+-- kernel-marked/zImage [2]
+-- rootfs.ext4
+-- rpi-firmware/
| +-- bootcode.bin
| +-- cmdline.txt
| +-- config.txt
| +-- fixup.dat
| `-- start.elf
+-- sdcard.img
`-- zImage
[1] Not all of them will be present, depending on the RaspberryPi
model you are using.
[2] This is the mkknlimg DT-marked kernel.
How to write the SD card
========================
Once the build process is finished you will have an image called "sdcard.img"
in the output/images/ directory.
Copy the bootable "sdcard.img" onto an SD card with "dd":
$ sudo dd if=output/images/sdcard.img of=/dev/sdX
Insert the SDcard into your Raspberry Pi, and power it up. Your new system
should come up now.