[Buildroot] [PATCH 1/2] boot/opensbi: allow building against an external platform

Richard Vodden <[email protected]>
Newsgroups net.busybox.buildroot
Message-ID <[email protected]> 
OpenSBI can build a platform that lives outside its source tree by
setting PLATFORM_DIR. For a board whose platform is not upstream, that
is considerably simpler than patching a platform directory into the
OpenSBI source or maintaining a custom tarball.

Replace the BR2_TARGET_OPENSBI_PLAT string with a choice of reference
platform, external platform, or no platform, and pass either PLATFORM or
PLATFORM_DIR accordingly. When PLATFORM is unset OpenSBI derives it from
the basename of PLATFORM_DIR and builds into build/platform/$(PLATFORM),
so OPENSBI_PLAT is set to that basename in order for the install step to
find the firmware. A trailing slash on the directory is stripped, as
$(notdir) would otherwise yield an empty string.

The three conditionals that previously tested BR2_TARGET_OPENSBI_PLAT
against the empty string now test !BR2_TARGET_OPENSBI_PLAT_NONE. Leaving
them referring to the removed symbol would have silently disabled
BR2_TARGET_OPENSBI_INSTALL_JUMP_IMG and INSTALL_DYNAMIC_IMG, producing
no firmware at all.

The in-tree defconfigs that set the old symbol are converted, and a
legacy entry carries an existing value over to the reference platform.

Signed-off-by: Richard Vodden <[email protected]>
---
 Config.in.legacy                        | 18 ++++++++
 boot/opensbi/Config.in                  | 55 +++++++++++++++++++------
 boot/opensbi/opensbi.mk                 | 16 +++++--
 configs/andes_ae350_45_defconfig        |  3 +-
 configs/hifive_unleashed_defconfig      |  3 +-
 configs/hifive_unmatched_defconfig      |  3 +-
 configs/nezha_defconfig                 |  3 +-
 configs/pine64_star64_defconfig         |  3 +-
 configs/qemu_riscv32_virt_defconfig     |  3 +-
 configs/qemu_riscv64_virt_defconfig     |  3 +-
 configs/sipeed_lichee_rv_defconfig      |  3 +-
 configs/sipeed_lichee_rv_dock_defconfig |  3 +-
 configs/sipeed_licheepi_4a_defconfig    |  3 +-
 configs/spike_riscv32_defconfig         |  3 +-
 configs/spike_riscv64_defconfig         |  3 +-
 configs/visionfive2_defconfig           |  3 +-
 16 files changed, 100 insertions(+), 28 deletions(-)

diff --git a/Config.in.legacy b/Config.in.legacy
index e2f9d9131f..ac451ee37c 100644
--- a/Config.in.legacy
+++ b/Config.in.legacy
@@ -146,6 +146,24 @@ endif
 
 comment "Legacy options removed in 2026.08"
 
+config BR2_TARGET_OPENSBI_PLAT
+	string "OpenSBI platform has been replaced"
+	help
+	  The OpenSBI platform is now selected with the "OpenSBI
+	  platform type" choice, which additionally allows building
+	  against a platform directory kept outside the OpenSBI source
+	  tree.
+
+	  Select "Reference platform" to keep the previous behaviour;
+	  the platform name has been carried over automatically.
+
+config BR2_TARGET_OPENSBI_PLAT_WRAP
+	bool
+	default y if BR2_TARGET_OPENSBI_PLAT != ""
+	select BR2_LEGACY
+
+# Note: BR2_TARGET_OPENSBI_PLAT is still referenced from boot/opensbi/Config.in
+
 config BR2_PACKAGE_TS4900_FPGA
 	bool "ts4900-fpga removed"
 	select BR2_LEGACY
diff --git a/boot/opensbi/Config.in b/boot/opensbi/Config.in
index 6e26da6344..2f4713b147 100644
--- a/boot/opensbi/Config.in
+++ b/boot/opensbi/Config.in
@@ -72,25 +72,56 @@ config BR2_TARGET_OPENSBI_LICENSE_FILES
 	  A space-separated list of license files related to the OpenSBI
 	  package.
 
-config BR2_TARGET_OPENSBI_PLAT
-	string "OpenSBI Platform"
-	default ""
+choice
+	prompt "OpenSBI platform type"
+	default BR2_TARGET_OPENSBI_PLAT_REF if BR2_TARGET_OPENSBI_PLAT != "" # legacy
+	default BR2_TARGET_OPENSBI_PLAT_NONE
+	help
+	  Select whether to build against a reference platform shipped
+	  with OpenSBI, or a platform directory kept outside the OpenSBI
+	  source tree.
+
+	  With "No platform", only the platform independent static
+	  library libsbi.a is built. Otherwise the platform specific
+	  library libplatsbi.a and the firmware examples are built too.
+
+config BR2_TARGET_OPENSBI_PLAT_REF
+	bool "Reference platform"
+
+config BR2_TARGET_OPENSBI_PLAT_EXT
+	bool "External platform"
+
+config BR2_TARGET_OPENSBI_PLAT_NONE
+	bool "No platform"
+
+endchoice
+
+config BR2_TARGET_OPENSBI_PLAT_REF_NAME
+	string "OpenSBI reference platform"
+	default BR2_TARGET_OPENSBI_PLAT if BR2_TARGET_OPENSBI_PLAT != "" # legacy
+	depends on BR2_TARGET_OPENSBI_PLAT_REF
+	help
+	  Name of a platform shipped with OpenSBI, as found under its
+	  platform/ directory, e.g. "generic".
+
+config BR2_TARGET_OPENSBI_PLAT_EXT_DIR
+	string "OpenSBI external platform directory"
+	depends on BR2_TARGET_OPENSBI_PLAT_EXT
 	help
-	  Specifies the OpenSBI platform to build. If no platform is
-	  specified only the OpenSBI platform independent static
-	  library libsbi.a is built. If a platform is specified then
-	  the platform specific static library libplatsbi.a and firmware
-	  examples are built.
+	  Path to an out-of-tree platform directory, passed to
+	  OpenSBI as PLATFORM_DIR. OpenSBI derives the platform
+	  name from its basename, so a trailing slash is tolerated
+	  but redundant.
 
 config BR2_TARGET_OPENSBI_INSTALL_DYNAMIC_IMG
 	bool "Install fw_dynamic image"
-	default y if BR2_TARGET_OPENSBI_PLAT != ""
+	default y if !BR2_TARGET_OPENSBI_PLAT_NONE
 	help
 	  This installs the fw_dynamic image.
 
 config BR2_TARGET_OPENSBI_INSTALL_JUMP_IMG
 	bool "Install fw_jump image"
-	default y if BR2_TARGET_OPENSBI_PLAT != ""
+	default y if !BR2_TARGET_OPENSBI_PLAT_NONE
 	help
 	  This installs the fw_jump image.
 
@@ -102,7 +133,7 @@ config BR2_TARGET_OPENSBI_INSTALL_PAYLOAD_IMG
 
 config BR2_TARGET_OPENSBI_LINUX_PAYLOAD
 	bool "Include Linux as OpenSBI Payload"
-	depends on BR2_TARGET_OPENSBI_PLAT != ""
+	depends on !BR2_TARGET_OPENSBI_PLAT_NONE
 	depends on BR2_LINUX_KERNEL
 	depends on BR2_LINUX_KERNEL_IMAGE
 	select BR2_TARGET_OPENSBI_INSTALL_PAYLOAD_IMG
@@ -111,7 +142,7 @@ config BR2_TARGET_OPENSBI_LINUX_PAYLOAD
 
 config BR2_TARGET_OPENSBI_UBOOT_PAYLOAD
 	bool "Include U-Boot as OpenSBI Payload"
-	depends on BR2_TARGET_OPENSBI_PLAT != ""
+	depends on !BR2_TARGET_OPENSBI_PLAT_NONE
 	depends on BR2_TARGET_UBOOT
 	select BR2_TARGET_OPENSBI_INSTALL_PAYLOAD_IMG
 	help
diff --git a/boot/opensbi/opensbi.mk b/boot/opensbi/opensbi.mk
index f9f550176f..8ca8a29894 100644
--- a/boot/opensbi/opensbi.mk
+++ b/boot/opensbi/opensbi.mk
@@ -32,11 +32,21 @@ OPENSBI_MAKE_ENV = \
 	CROSS_COMPILE=$(TARGET_CROSS) \
 	$(call qstrip,$(BR2_TARGET_OPENSBI_ADDITIONAL_VARIABLES))
 
-OPENSBI_PLAT = $(call qstrip,$(BR2_TARGET_OPENSBI_PLAT))
-ifneq ($(OPENSBI_PLAT),)
+ifeq ($(BR2_TARGET_OPENSBI_PLAT_REF),y)
+OPENSBI_PLAT = $(call qstrip,$(BR2_TARGET_OPENSBI_PLAT_REF_NAME))
 OPENSBI_MAKE_ENV += PLATFORM=$(OPENSBI_PLAT)
 endif
 
+# OpenSBI derives PLATFORM from $(basename PLATFORM_DIR) when PLATFORM is unset,
+# and builds into build/platform/$(PLATFORM)/ -- so OPENSBI_PLAT must match that
+# for the install step below to find the firmware. patsubst strips any trailing
+# slash, which would otherwise make notdir return an empty string.
+ifeq ($(BR2_TARGET_OPENSBI_PLAT_EXT),y)
+OPENSBI_PLAT_EXT_DIR = $(patsubst %/,%,$(call qstrip,$(BR2_TARGET_OPENSBI_PLAT_EXT_DIR)))
+OPENSBI_PLAT = $(notdir $(OPENSBI_PLAT_EXT_DIR))
+OPENSBI_MAKE_ENV += PLATFORM_DIR=$(OPENSBI_PLAT_EXT_DIR)
+endif
+
 ifeq ($(BR2_TARGET_OPENSBI_LINUX_PAYLOAD),y)
 OPENSBI_DEPENDENCIES += linux
 OPENSBI_MAKE_ENV += FW_PAYLOAD_PATH="$(BINARIES_DIR)/Image"
@@ -69,7 +79,7 @@ OPENSBI_INSTALL_IMAGES = YES
 OPENSBI_FW_IMAGES += payload
 endif
 
-ifneq ($(OPENSBI_PLAT),)
+ifneq ($(BR2_TARGET_OPENSBI_PLAT_NONE),y)
 define OPENSBI_INSTALL_IMAGES_CMDS
 	$(foreach f,$(OPENSBI_FW_IMAGES),\
 		$(INSTALL) -m 0644 -D $(@D)/build/platform/$(OPENSBI_PLAT)/firmware/fw_$(f).bin \
diff --git a/configs/andes_ae350_45_defconfig b/configs/andes_ae350_45_defconfig
index 80b780b6e0..a70b228155 100644
--- a/configs/andes_ae350_45_defconfig
+++ b/configs/andes_ae350_45_defconfig
@@ -21,7 +21,8 @@ BR2_TARGET_ROOTFS_EXT2_4=y
 BR2_TARGET_OPENSBI=y
 BR2_TARGET_OPENSBI_CUSTOM_VERSION=y
 BR2_TARGET_OPENSBI_CUSTOM_VERSION_VALUE="1.6"
-BR2_TARGET_OPENSBI_PLAT="generic"
+BR2_TARGET_OPENSBI_PLAT_REF=y
+BR2_TARGET_OPENSBI_PLAT_REF_NAME="generic"
 # BR2_TARGET_OPENSBI_INSTALL_JUMP_IMG is not set
 BR2_TARGET_UBOOT=y
 BR2_TARGET_UBOOT_BUILD_SYSTEM_KCONFIG=y
diff --git a/configs/hifive_unleashed_defconfig b/configs/hifive_unleashed_defconfig
index e83af773f7..3771dd2ad0 100644
--- a/configs/hifive_unleashed_defconfig
+++ b/configs/hifive_unleashed_defconfig
@@ -27,7 +27,8 @@ BR2_TARGET_ROOTFS_EXT2_4=y
 BR2_TARGET_OPENSBI=y
 BR2_TARGET_OPENSBI_CUSTOM_VERSION=y
 BR2_TARGET_OPENSBI_CUSTOM_VERSION_VALUE="1.2"
-BR2_TARGET_OPENSBI_PLAT="generic"
+BR2_TARGET_OPENSBI_PLAT_REF=y
+BR2_TARGET_OPENSBI_PLAT_REF_NAME="generic"
 BR2_TARGET_UBOOT=y
 BR2_TARGET_UBOOT_BUILD_SYSTEM_KCONFIG=y
 BR2_TARGET_UBOOT_CUSTOM_VERSION=y
diff --git a/configs/hifive_unmatched_defconfig b/configs/hifive_unmatched_defconfig
index 0b63ce15ff..b4ac91c557 100644
--- a/configs/hifive_unmatched_defconfig
+++ b/configs/hifive_unmatched_defconfig
@@ -27,7 +27,8 @@ BR2_TARGET_ROOTFS_EXT2_4=y
 BR2_TARGET_OPENSBI=y
 BR2_TARGET_OPENSBI_CUSTOM_VERSION=y
 BR2_TARGET_OPENSBI_CUSTOM_VERSION_VALUE="1.2"
-BR2_TARGET_OPENSBI_PLAT="generic"
+BR2_TARGET_OPENSBI_PLAT_REF=y
+BR2_TARGET_OPENSBI_PLAT_REF_NAME="generic"
 BR2_TARGET_UBOOT=y
 BR2_TARGET_UBOOT_BUILD_SYSTEM_KCONFIG=y
 BR2_TARGET_UBOOT_CUSTOM_VERSION=y
diff --git a/configs/nezha_defconfig b/configs/nezha_defconfig
index c234b3e243..914b362e22 100644
--- a/configs/nezha_defconfig
+++ b/configs/nezha_defconfig
@@ -21,7 +21,8 @@ BR2_TARGET_ROOTFS_EXT2_4=y
 BR2_TARGET_OPENSBI=y
 BR2_TARGET_OPENSBI_CUSTOM_VERSION=y
 BR2_TARGET_OPENSBI_CUSTOM_VERSION_VALUE="1.4"
-BR2_TARGET_OPENSBI_PLAT="generic"
+BR2_TARGET_OPENSBI_PLAT_REF=y
+BR2_TARGET_OPENSBI_PLAT_REF_NAME="generic"
 # BR2_TARGET_OPENSBI_INSTALL_JUMP_IMG is not set
 BR2_TARGET_UBOOT=y
 BR2_TARGET_UBOOT_BUILD_SYSTEM_KCONFIG=y
diff --git a/configs/pine64_star64_defconfig b/configs/pine64_star64_defconfig
index a0356447d5..88b20bfee3 100644
--- a/configs/pine64_star64_defconfig
+++ b/configs/pine64_star64_defconfig
@@ -17,7 +17,8 @@ BR2_TARGET_ROOTFS_EXT2=y
 BR2_TARGET_ROOTFS_EXT2_4=y
 BR2_TARGET_ROOTFS_EXT2_SIZE="100M"
 BR2_TARGET_OPENSBI=y
-BR2_TARGET_OPENSBI_PLAT="generic"
+BR2_TARGET_OPENSBI_PLAT_REF=y
+BR2_TARGET_OPENSBI_PLAT_REF_NAME="generic"
 # BR2_TARGET_OPENSBI_INSTALL_JUMP_IMG is not set
 BR2_TARGET_UBOOT=y
 BR2_TARGET_UBOOT_BUILD_SYSTEM_KCONFIG=y
diff --git a/configs/qemu_riscv32_virt_defconfig b/configs/qemu_riscv32_virt_defconfig
index a57c94910c..714e5ec63a 100644
--- a/configs/qemu_riscv32_virt_defconfig
+++ b/configs/qemu_riscv32_virt_defconfig
@@ -14,6 +14,7 @@ BR2_TARGET_ROOTFS_EXT2=y
 BR2_TARGET_OPENSBI=y
 BR2_TARGET_OPENSBI_CUSTOM_VERSION=y
 BR2_TARGET_OPENSBI_CUSTOM_VERSION_VALUE="1.6"
-BR2_TARGET_OPENSBI_PLAT="generic"
+BR2_TARGET_OPENSBI_PLAT_REF=y
+BR2_TARGET_OPENSBI_PLAT_REF_NAME="generic"
 BR2_PACKAGE_HOST_QEMU=y
 BR2_PACKAGE_HOST_QEMU_SYSTEM_MODE=y
diff --git a/configs/qemu_riscv64_virt_defconfig b/configs/qemu_riscv64_virt_defconfig
index 0d91971d1c..91b49068af 100644
--- a/configs/qemu_riscv64_virt_defconfig
+++ b/configs/qemu_riscv64_virt_defconfig
@@ -13,6 +13,7 @@ BR2_TARGET_ROOTFS_EXT2=y
 BR2_TARGET_OPENSBI=y
 BR2_TARGET_OPENSBI_CUSTOM_VERSION=y
 BR2_TARGET_OPENSBI_CUSTOM_VERSION_VALUE="1.6"
-BR2_TARGET_OPENSBI_PLAT="generic"
+BR2_TARGET_OPENSBI_PLAT_REF=y
+BR2_TARGET_OPENSBI_PLAT_REF_NAME="generic"
 BR2_PACKAGE_HOST_QEMU=y
 BR2_PACKAGE_HOST_QEMU_SYSTEM_MODE=y
diff --git a/configs/sipeed_lichee_rv_defconfig b/configs/sipeed_lichee_rv_defconfig
index 750d2d6e3b..eba7777bf5 100644
--- a/configs/sipeed_lichee_rv_defconfig
+++ b/configs/sipeed_lichee_rv_defconfig
@@ -16,7 +16,8 @@ BR2_TARGET_ROOTFS_EXT2_4=y
 BR2_TARGET_OPENSBI=y
 BR2_TARGET_OPENSBI_CUSTOM_VERSION=y
 BR2_TARGET_OPENSBI_CUSTOM_VERSION_VALUE="1.2"
-BR2_TARGET_OPENSBI_PLAT="generic"
+BR2_TARGET_OPENSBI_PLAT_REF=y
+BR2_TARGET_OPENSBI_PLAT_REF_NAME="generic"
 # BR2_TARGET_OPENSBI_INSTALL_JUMP_IMG is not set
 BR2_TARGET_UBOOT=y
 BR2_TARGET_UBOOT_BUILD_SYSTEM_KCONFIG=y
diff --git a/configs/sipeed_lichee_rv_dock_defconfig b/configs/sipeed_lichee_rv_dock_defconfig
index 8c8dd2771b..56ef107086 100644
--- a/configs/sipeed_lichee_rv_dock_defconfig
+++ b/configs/sipeed_lichee_rv_dock_defconfig
@@ -24,7 +24,8 @@ BR2_TARGET_ROOTFS_EXT2_4=y
 BR2_TARGET_OPENSBI=y
 BR2_TARGET_OPENSBI_CUSTOM_VERSION=y
 BR2_TARGET_OPENSBI_CUSTOM_VERSION_VALUE="1.2"
-BR2_TARGET_OPENSBI_PLAT="generic"
+BR2_TARGET_OPENSBI_PLAT_REF=y
+BR2_TARGET_OPENSBI_PLAT_REF_NAME="generic"
 # BR2_TARGET_OPENSBI_INSTALL_JUMP_IMG is not set
 BR2_TARGET_UBOOT=y
 BR2_TARGET_UBOOT_BUILD_SYSTEM_KCONFIG=y
diff --git a/configs/sipeed_licheepi_4a_defconfig b/configs/sipeed_licheepi_4a_defconfig
index c7867ed05d..e57536c7fe 100644
--- a/configs/sipeed_licheepi_4a_defconfig
+++ b/configs/sipeed_licheepi_4a_defconfig
@@ -30,7 +30,8 @@ BR2_TARGET_OPENSBI=y
 BR2_TARGET_OPENSBI_CUSTOM_GIT=y
 BR2_TARGET_OPENSBI_CUSTOM_REPO_URL="https://github.com/revyos/thead-opensbi.git"
 BR2_TARGET_OPENSBI_CUSTOM_REPO_VERSION="61d7484c752a5e4c464d5dc18e21d9ac67fbbefa"
-BR2_TARGET_OPENSBI_PLAT="generic"
+BR2_TARGET_OPENSBI_PLAT_REF=y
+BR2_TARGET_OPENSBI_PLAT_REF_NAME="generic"
 BR2_TARGET_UBOOT=y
 BR2_TARGET_UBOOT_BOARDNAME="light_lpi4a"
 BR2_TARGET_UBOOT_CUSTOM_GIT=y
diff --git a/configs/spike_riscv32_defconfig b/configs/spike_riscv32_defconfig
index a73f335f34..22a1d34446 100644
--- a/configs/spike_riscv32_defconfig
+++ b/configs/spike_riscv32_defconfig
@@ -12,6 +12,7 @@ BR2_TARGET_ROOTFS_CPIO=y
 BR2_TARGET_OPENSBI=y
 BR2_TARGET_OPENSBI_CUSTOM_VERSION=y
 BR2_TARGET_OPENSBI_CUSTOM_VERSION_VALUE="1.6"
-BR2_TARGET_OPENSBI_PLAT="generic"
+BR2_TARGET_OPENSBI_PLAT_REF=y
+BR2_TARGET_OPENSBI_PLAT_REF_NAME="generic"
 BR2_TARGET_OPENSBI_LINUX_PAYLOAD=y
 BR2_PACKAGE_HOST_RISCV_ISA_SIM=y
diff --git a/configs/spike_riscv64_defconfig b/configs/spike_riscv64_defconfig
index 7b698737e2..feedc9b2a8 100644
--- a/configs/spike_riscv64_defconfig
+++ b/configs/spike_riscv64_defconfig
@@ -11,6 +11,7 @@ BR2_TARGET_ROOTFS_CPIO=y
 BR2_TARGET_OPENSBI=y
 BR2_TARGET_OPENSBI_CUSTOM_VERSION=y
 BR2_TARGET_OPENSBI_CUSTOM_VERSION_VALUE="1.6"
-BR2_TARGET_OPENSBI_PLAT="generic"
+BR2_TARGET_OPENSBI_PLAT_REF=y
+BR2_TARGET_OPENSBI_PLAT_REF_NAME="generic"
 BR2_TARGET_OPENSBI_LINUX_PAYLOAD=y
 BR2_PACKAGE_HOST_RISCV_ISA_SIM=y
diff --git a/configs/visionfive2_defconfig b/configs/visionfive2_defconfig
index 8223e6faa1..0cbe61c2b1 100644
--- a/configs/visionfive2_defconfig
+++ b/configs/visionfive2_defconfig
@@ -20,7 +20,8 @@ BR2_TARGET_ROOTFS_EXT2_4=y
 BR2_TARGET_OPENSBI=y
 BR2_TARGET_OPENSBI_CUSTOM_VERSION=y
 BR2_TARGET_OPENSBI_CUSTOM_VERSION_VALUE="1.6"
-BR2_TARGET_OPENSBI_PLAT="generic"
+BR2_TARGET_OPENSBI_PLAT_REF=y
+BR2_TARGET_OPENSBI_PLAT_REF_NAME="generic"
 # BR2_TARGET_OPENSBI_INSTALL_JUMP_IMG is not set
 BR2_TARGET_OPENSBI_ADDITIONAL_VARIABLES="FW_TEXT_START=0x40000000 FW_OPTIONS=0"
 BR2_TARGET_UBOOT=y
-- 
2.43.0

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