[Buildroot] [PATCH v2] raspberrypi, raspberrypi2: add a serial console
Luca Ceresoli
luca at lucaceresoli.net
Mon Apr 18 11:51:41 UTC 2016
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 at free.fr>
>> Cc: Arnout Vandecappelle <arnout at mind.be>
>> Signed-off-by: Luca Ceresoli <luca at 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,
--
Luca
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