[Buildroot] [PATCH] raspberrypi, raspberrypi2: add a serial console

Luca Ceresoli luca at lucaceresoli.net
Mon Mar 28 22:08:17 UTC 2016


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 two changes:
 1. have two 'console=' entries in the kernel command line;
 2. add a new getty process to the generated inittab.

Step 2 requires a post-build script since the Buildroot makefiles can
configure only one console. But instead of simply adding a new getty
on ttyAMA0 (which would work) this patch actually changes
BR2_TARGET_GENERIC_GETTY_PORT from tty1 to ttyAMA0, 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:

  ttyAMA0::respawn:/sbin/getty -L  ttyAMA0 0 vt100 # GENERIC_SERIAL
  tty1::respawn:/sbin/getty -L  tty1 0 vt100 # HDMI console

Cc: Yann E. MORIN <yann.morin.1998 at free.fr>
Signed-off-by: Luca Ceresoli <luca at lucaceresoli.net>

---

Tested on both Raspberry Pi B and Raspberry Pi 2, each on serial and
HDMI console.
---
 board/raspberrypi/post-build.sh  | 9 +++++++++
 configs/raspberrypi2_defconfig   | 3 ++-
 configs/raspberrypi_defconfig    | 3 ++-
 package/rpi-firmware/cmdline.txt | 2 +-
 4 files changed, 14 insertions(+), 3 deletions(-)
 create mode 100755 board/raspberrypi/post-build.sh

diff --git a/board/raspberrypi/post-build.sh b/board/raspberrypi/post-build.sh
new file mode 100755
index 000000000000..7eae14a88569
--- /dev/null
+++ b/board/raspberrypi/post-build.sh
@@ -0,0 +1,9 @@
+#!/bin/sh
+
+set -u
+set -e
+
+# Add a console on tty1
+grep -qE '^tty1::' ${TARGET_DIR}/etc/inittab || \
+sed -i '/GENERIC_SERIAL/a\
+tty1::respawn:/sbin/getty -L  tty1 0 vt100 # HDMI console' ${TARGET_DIR}/etc/inittab
diff --git a/configs/raspberrypi2_defconfig b/configs/raspberrypi2_defconfig
index ce41ee31adba..0ffc6cdaf158 100644
--- a/configs/raspberrypi2_defconfig
+++ b/configs/raspberrypi2_defconfig
@@ -5,7 +5,7 @@ BR2_ARM_FPU_NEON_VFPV4=y
 
 BR2_TOOLCHAIN_BUILDROOT_CXX=y
 
-BR2_TARGET_GENERIC_GETTY_PORT="tty1"
+BR2_TARGET_GENERIC_GETTY_PORT="ttyAMA0"
 
 # Linux headers same as kernel, a 4.1 series
 BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_4_1=y
@@ -33,4 +33,5 @@ BR2_PACKAGE_HOST_MTOOLS=y
 BR2_TARGET_ROOTFS_EXT2=y
 BR2_TARGET_ROOTFS_EXT2_4=y
 # BR2_TARGET_ROOTFS_TAR is not set
+BR2_ROOTFS_POST_BUILD_SCRIPT="board/raspberrypi2/post-build.sh"
 BR2_ROOTFS_POST_IMAGE_SCRIPT="board/raspberrypi2/post-image.sh"
diff --git a/configs/raspberrypi_defconfig b/configs/raspberrypi_defconfig
index 3b3cc504c2be..717d798b3851 100644
--- a/configs/raspberrypi_defconfig
+++ b/configs/raspberrypi_defconfig
@@ -2,7 +2,7 @@ BR2_arm=y
 BR2_arm1176jzf_s=y
 BR2_ARM_EABIHF=y
 
-BR2_TARGET_GENERIC_GETTY_PORT="tty1"
+BR2_TARGET_GENERIC_GETTY_PORT="ttyAMA0"
 
 # Linux headers same as kernel, a 4.1 series
 BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_4_1=y
@@ -32,4 +32,5 @@ BR2_PACKAGE_HOST_MTOOLS=y
 BR2_TARGET_ROOTFS_EXT2=y
 BR2_TARGET_ROOTFS_EXT2_4=y
 # BR2_TARGET_ROOTFS_TAR is not set
+BR2_ROOTFS_POST_BUILD_SCRIPT="board/raspberrypi/post-build.sh"
 BR2_ROOTFS_POST_IMAGE_SCRIPT="board/raspberrypi/post-image.sh"
diff --git a/package/rpi-firmware/cmdline.txt b/package/rpi-firmware/cmdline.txt
index 38aa3782621b..155a54693bff 100644
--- a/package/rpi-firmware/cmdline.txt
+++ b/package/rpi-firmware/cmdline.txt
@@ -1 +1 @@
-root=/dev/mmcblk0p2 rootwait
+root=/dev/mmcblk0p2 rootwait console=tty1 console=ttyAMA0,115200
-- 
1.9.1



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