[v2] raspberrypi, raspberrypi2: add a serial console

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>

---

v2:
 - remove BR2_TARGET_GENERIC_GETTY_PORT, it defaults to "console"
 - rebase on current master

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   | 2 +-
 configs/raspberrypi_defconfig    | 2 +-
 package/rpi-firmware/cmdline.txt | 2 +-
 4 files changed, 12 insertions(+), 3 deletions(-)
 create mode 100755 board/raspberrypi/post-build.sh

Luca, All,

On 2016-04-17 23:45 +0200, Luca Ceresoli spake thusly:
> 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>

Regards,
Yann E. MORIN.

> ---
> 
> v2:
>  - remove BR2_TARGET_GENERIC_GETTY_PORT, it defaults to "console"
>  - rebase on current master
> 
> 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   | 2 +-
>  configs/raspberrypi_defconfig    | 2 +-
>  package/rpi-firmware/cmdline.txt | 2 +-
>  4 files changed, 12 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 506330cd0780..7fc39c234c32 100644
> --- a/configs/raspberrypi2_defconfig
> +++ b/configs/raspberrypi2_defconfig
> @@ -5,7 +5,6 @@ BR2_ARM_FPU_NEON_VFPV4=y
>  
>  BR2_TOOLCHAIN_BUILDROOT_CXX=y
>  
> -BR2_TARGET_GENERIC_GETTY_PORT="tty1"
>  BR2_SYSTEM_DHCP="eth0"
>  
>  # Linux headers same as kernel, a 4.1 series
> @@ -33,4 +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/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 1795b2c03d53..8d13381105c1 100644
> --- a/configs/raspberrypi_defconfig
> +++ b/configs/raspberrypi_defconfig
> @@ -2,7 +2,6 @@ BR2_arm=y
>  BR2_arm1176jzf_s=y
>  BR2_ARM_EABIHF=y
>  
> -BR2_TARGET_GENERIC_GETTY_PORT="tty1"
>  BR2_SYSTEM_DHCP="eth0"
>  
>  # Linux headers same as kernel, a 4.1 series
> @@ -32,4 +31,5 @@ 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
>

Hello,

On Sun, 17 Apr 2016 23:45:46 +0200, Luca Ceresoli wrote:
> 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>
> 
> ---

Applied to master, thanks. Maybe this calls for an update of the
RaspberryPi readme.txt file, to explicitly indicate that a getty will
be running on both the HDMI/composite output *and* the serial port?

Thanks!

Thomas

Dear Thomas,

On 18/04/2016 13:37, Thomas Petazzoni wrote:
> Hello,
> 
> On Sun, 17 Apr 2016 23:45:46 +0200, Luca Ceresoli wrote:
>> 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>
>>
>> ---
> 
> Applied to master, thanks. Maybe this calls for an update of the
> RaspberryPi readme.txt file, to explicitly indicate that a getty will
> be running on both the HDMI/composite output *and* the serial port?

Indeed a good suggestion! I'll have a look.

Thanks,