[Buildroot] [PATCH 2/6] boot/uboot: support building U-Boot with Python 3.x

[Thomas Petazzoni <thomas.petazzoni@bootlin.com>]

U-Boot versions newer than 2020.01 use Python 3.x instead of Python
2.x in various scripts.

We already had the BR2_TARGET_UBOOT_NEEDS_PYLIBFDT and
BR2_TARGET_UBOOT_NEEDS_PYELFTOOLS options, but depending on the U-Boot
version, we now need to indicate if Python 2.x or Python 3.x should be
used.

In addition, it turns out that some U-Boot configurations need a
Python interpreter, without needing pylibfdt or pyelftools. Some of
our defconfigs were abusing the BR2_TARGET_UBOOT_NEEDS_PYLIBFDT option
to make sure a Python interpreter was built.

To solve both issues, we add a new option
BR2_TARGET_UBOOT_NEEDS_PYTHON, which itself has a choice to choose
between Python 2.x and Python 3.x. It defaults to Python 2.x to
preserve backward compatibility.

The existing BR2_TARGET_UBOOT_NEEDS_PYLIBFDT and
BR2_TARGET_UBOOT_NEEDS_PYELFTOOLS options select
BR2_TARGET_UBOOT_NEEDS_PYTHON.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
---
 boot/uboot/Config.in | 29 +++++++++++++++++++++++++++++
 boot/uboot/uboot.mk  | 12 +++++++++++-
 2 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/boot/uboot/Config.in b/boot/uboot/Config.in
index 7a6f5053fd..e10166a113 100644
--- a/boot/uboot/Config.in
+++ b/boot/uboot/Config.in
@@ -147,14 +147,43 @@ config BR2_TARGET_UBOOT_NEEDS_DTC
 	  Select this option if your U-Boot board configuration
 	  requires the Device Tree compiler to be available.
 
+config BR2_TARGET_UBOOT_NEEDS_PYTHON
+	bool "U-Boot needs host Python"
+
+if BR2_TARGET_UBOOT_NEEDS_PYTHON
+
+choice
+	prompt "Python version"
+	default BR2_TARGET_UBOOT_NEEDS_PYTHON2
+
+config BR2_TARGET_UBOOT_NEEDS_PYTHON2
+	bool "python 2.x"
+	help
+	  Select this option if U-Boot needs a host Python 2.x
+	  interpreter. This is the case for some U-Boot
+	  configurations, prior to U-Boot 2020.01.
+
+config BR2_TARGET_UBOOT_NEEDS_PYTHON3
+	bool "python 3.x"
+	help
+	  Select this option if U-Boot needs a host Python 3.x
+	  interpreter. This is the case for some U-Boot
+	  configurations, after U-Boot 2020.01.
+
+endchoice
+
+endif
+
 config BR2_TARGET_UBOOT_NEEDS_PYLIBFDT
 	bool "U-Boot needs pylibfdt"
+	select BR2_TARGET_UBOOT_NEEDS_PYTHON
 	help
 	  Select this option if your U-Boot board configuration
 	  requires the Python libfdt library to be available.
 
 config BR2_TARGET_UBOOT_NEEDS_PYELFTOOLS
 	bool "U-Boot needs pyelftools"
+	select BR2_TARGET_UBOOT_NEEDS_PYTHON
 	help
 	  Select this option if your U-Boot board configuration
 	  requires the Python pyelftools library to be available.
diff --git a/boot/uboot/uboot.mk b/boot/uboot/uboot.mk
index 7bd9cbae52..1d50e72846 100644
--- a/boot/uboot/uboot.mk
+++ b/boot/uboot/uboot.mk
@@ -159,12 +159,22 @@ ifeq ($(BR2_TARGET_UBOOT_NEEDS_DTC),y)
 UBOOT_DEPENDENCIES += host-dtc
 endif
 
+ifeq ($(BR2_TARGET_UBOOT_NEEDS_PYTHON2),y)
+UBOOT_DEPENDENCIES += host-python
+else ifeq ($(BR2_TARGET_UBOOT_NEEDS_PYTHON3),y)
+UBOOT_DEPENDENCIES += host-python3
+endif
+
 ifeq ($(BR2_TARGET_UBOOT_NEEDS_PYLIBFDT),y)
-UBOOT_DEPENDENCIES += host-python host-swig
+UBOOT_DEPENDENCIES += host-swig
 endif
 
 ifeq ($(BR2_TARGET_UBOOT_NEEDS_PYELFTOOLS),y)
+ifeq ($(BR2_TARGET_UBOOT_NEEDS_PYTHON2),y)
 UBOOT_DEPENDENCIES += host-python-pyelftools
+else ifeq ($(BR2_TARGET_UBOOT_NEEDS_PYTHON3),y)
+UBOOT_DEPENDENCIES += host-python3-pyelftools
+endif
 endif
 
 ifeq ($(BR2_TARGET_UBOOT_NEEDS_OPENSSL),y)
-- 
2.26.2