bcm53xx: put kernel into TRX when building initramfs images

Many (most?) devices can't boot raw kernel using tftp and probably none
allows flashing it. It's way more usable to have TRX with kernel
containing initrams as such an image can be actually flashed.

An exception are Buffalo devices which have recovery mode with support
for booting kernels over TFTP. For them keep building default images.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>

target/linux/bcm53xx/image/Makefile

@@ -49,6 +49,15 @@ define Build/buffalo-wzr-header
 	mv $@.new $@
 endef
 
+# TRX with only one (kernel) partition
+define Build/trx
+	$(STAGING_DIR_HOST)/bin/trx \
+		-o $@.new \
+		-m 33554432 \
+		-f $@
+	mv $@.new $@
+endef
+
 define Build/trx-serial
 	$(STAGING_DIR_HOST)/bin/trx \
 		-o $@.new \
@@ -111,6 +120,8 @@ define Device/Default
   DEVICE_DTS := $(patsubst %.dtb,%,$(notdir $(wildcard $(if $(IB),$(KDIR),$(DTS_DIR))/*-$(1).dtb)))
   KERNEL := kernel-bin | append-dtb | lzma-d16
   KERNEL_DEPENDS = $$(wildcard $(DTS_DIR)/$$(DEVICE_DTS).dts)
+  KERNEL_INITRAMFS_SUFFIX := .trx
+  KERNEL_INITRAMFS := kernel-bin | append-dtb | lzma-d16 | trx
   FILESYSTEMS := squashfs
   KERNEL_NAME := zImage
   IMAGE_NAME = $$(IMAGE_PREFIX)-$$(1).$$(2)
@@ -149,19 +160,32 @@ define Device/asus-rt-n18u
 endef
 TARGET_DEVICES += asus-rt-n18u
 
+# Buffalo devices have TFTP recovery mode which can work nicely with initramfs
+# kernels.
+# We should have two initramfs images for Buffalo: plain initramfs kernel and
+# TRX with initramfs kernel. It's not possible right now so let's just build
+# plain initramfs kernel as it may be more useful.
+define Device/buffalo/Default
+  KERNEL_INITRAMFS_SUFFIX = $$(KERNEL_SUFFIX)
+  KERNEL_INITRAMFS = $$(KERNEL)
+endef
+
 define Device/buffalo-wxr-1900dhp
+  $(call Device/buffalo/Default)
   DEVICE_TITLE := Buffalo WXR-1900DHP
   DEVICE_PACKAGES := $(USB3_PACKAGES)
 endef
 TARGET_DEVICES += buffalo-wxr-1900dhp
 
 define Device/buffalo-wzr-600dhp2
+  $(call Device/buffalo/Default)
   DEVICE_TITLE := Buffalo WZR-600DHP2
   DEVICE_PACKAGES := kmod-b43 $(USB2_PACKAGES)
 endef
 TARGET_DEVICES += buffalo-wzr-600dhp2
 
 define Device/buffalo-wzr-900dhp
+  $(call Device/buffalo/Default)
   DEVICE_TITLE := Buffalo WZR-900DHP
   DEVICE_PACKAGES := kmod-b43 $(USB3_PACKAGES)
   BUFFALO_TAG_PLATFORM := bcm
@@ -182,6 +206,7 @@ endef
 TARGET_DEVICES += buffalo-wzr-900dhp
 
 define Device/buffalo-wzr-1750dhp
+  $(call Device/buffalo/Default)
   DEVICE_TITLE := Buffalo WZR-1750DHP
   DEVICE_PACKAGES := kmod-b43 $(USB3_PACKAGES)
 endef