Re: [HELP] Barebox porting

From: Sascha Hauer <s.hauer@pengutronix.de>
To: "Серафим Долбилов" <s.dlblv@ya.ru>
Cc: Barebox List <barebox@lists.infradead.org>
Subject: Re: [HELP] Barebox porting
Date: Wed, 9 Jan 2019 14:03:41 +0100	[thread overview]
Message-ID: <20190109130341.sxiqrcg43mxuzrai@pengutronix.de> (raw)
In-Reply-To: <87941547037637@iva6-19b25c513db4.qloud-c.yandex.net>

Hi,

On Wed, Jan 09, 2019 at 03:40:37PM +0300, Серафим Долбилов wrote:
> Hi, I'm trying to add my own custom board support to barebox. It's based on i.MX6ULL CPU.
> So, I have the following questions:
> 
> * Why does the config parameter IMX_MULTI_BOARDS exist? Why such
> boards as EUKREA CPUIMX35 and i.MX53 SMD are isolated from the others?
> So, if I add custom board, which class it must share? "Isolated" or
> "mainline"?

barebox can be built for multiple boards in a single build, referred to
as multi image support. This needs some support by the board code,
specifically it has use device tree rather than platform support. Some
boards do not support this and are in the !IMX_MULTI_BOARDS section.

For new boards you should use IMX_MULTI_BOARDS.

> * AFAIK, one of main Barebox advantages is that it can use the only DT
> for both itself and Linux kernel. I'm interested in how is this
> behaviour realized in practice. How can I use the only DTS for Barebox
> and pass it to Linux kernel on its boot?

barebox will pass the DTB (not DTS) it is probed with to the kernel
automatically. Nothing to do here.

> * I need some help with structure of images/Makefile.imx file. I cannot make any sense in why pblx-*, CFG-*, FILE-* targets are used and how does it everything interact in resulting image.

Some documentation is at the top of images/Makefile.

As an example take the realq7 entry:

pblb-$(CONFIG_MACH_REALQ7) += start_imx6_realq7
CFG_start_imx6_realq7.pblb.imximg = $(board)/datamodul-edm-qmx6/flash-header.imxcfg
FILE_barebox-datamodul-edm-qmx6.img = start_imx6_realq7.pblb.imximg
image-$(CONFIG_MACH_REALQ7) += barebox-datamodul-edm-qmx6.img

CONFIG_MACH_REALQ7 should be replaced by your own Kconfig board name.
start_imx6_realq7 is the name of the entry function, should be replaced
with whatever you pass to your ENTRY_FUNCTION macro. CFG_* should point
to your flash header config file. The resulting image will be called
barebox-datamodul-edm-qmx6.img in this example.

Hope that helps.

Sascha

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