So far, the compatibility mechanism only works if both device and
image are already updated to the new routines. This patch extends
the sysupgrade metadata and fwtool_check_image() to account for
"older" images as well:
The basic mechanism for older devices to check for image compatibility
is the supported_devices entry. This can be exploited by putting
a custom message into this variable of the metadata, so older FW
will produce a mismatch and print the message as it thinks it's the
list of supported devices. So, we have two cases:
device 1.0, image 1.0:
The metadata will just contain supported_devices as before.
device 1.0, image 1.1:
The metadata will contain:
"new_supported_devices":["device_string1", "device_string2", ...],
"supported_devices":["Image version 1.1 incompatible to device: ..."]
If the device is "legacy", i.e. does not have the updated fwtool.sh,
it will just fail with image check and print the content of
supported_devices. If DEVICE_COMPAT_MESSAGE is set, this will be
printed on old devices as well through the same mechanism. Otherwise
a generic "Please check documentation ..." is appended.
Upgrade can still be performed with -F like when
SUPPORTED_DEVICES has been removed to prevent bricking.
If the device has updated fwtool.sh (but is 1.0), it will just use
the new_supported_devices instead, and work as intended (flashing
with -n will work, flashing without will print the appropriate
warning).
This mechanism should provide a fair tradeoff between simplicity
and functionality.
Since we touched a lot of fields in metadata, this also bumps
metadata_version to 1.1.
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>
02d6ac1060