Unable to find rootfs after kernel_menuconfig

Rogier Lodewijks

In the pursuit to track down my SPI issues I've reconfigured my kernel to not include the mt7621 SPI HW driver.

The patch to the .config is almost trivially simple:

diff --git a/target/linux/ramips/mt7688/config-4.4 b/target/linux/ramips/mt7688/config-4.4
index c4a844da38..6fc9a91e6d 100644
--- a/target/linux/ramips/mt7688/config-4.4
+++ b/target/linux/ramips/mt7688/config-4.4
@@ -225,8 +225,11 @@ CONFIG_SOC_MT7620=y
 # CONFIG_SOC_RT3883 is not set
 CONFIG_SOUND=m
 CONFIG_SPI=y
+CONFIG_SPI_BITBANG=y
+CONFIG_SPI_DEBUG=y
+CONFIG_SPI_GPIO=y
 CONFIG_SPI_MASTER=y
-CONFIG_SPI_MT7621=y
+# CONFIG_SPI_MT7621 is not set
 # CONFIG_SPI_RT2880 is not set
 CONFIG_SRCU=y
 CONFIG_SWCONFIG=y

Building a new image works fine, but the resulting image -somehow- is not booting. I did not touch anything other that the patch above. Here is the kernel boot output deemed important:

[    0.000000] Kernel command line: console=ttyS0,115200 rootfstype=squashfs,jffs2

**snip**

[    0.435122] VFS: Cannot open root device "(null)" or unknown-block(0,0): error -6
[    0.442720] Please append a correct "root=" boot option; here are the available partitions:
[    0.451254] Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)
[    0.460532] Rebooting in 1 seconds..

Seemingly the kernel is not correctly pointed towards the rootfs. Isn't it u-boot's job to inform the kernel of the whereabouts of the rootfs and the layout of the MTD main storage device?

Me not (yet :)) being an OpwnWRT/Buildroot expert, it's probably something trivial I'm overlooking here. Any handles anyone?