When building this with clang, we get a warning such as:
cmd/bootflow.c:412:27: warning: variable 'bflow' is uninitialized when used here [-Wuninitialized]
        printf("Selected: %s\n", bflow->os_name ? bflow->os_name : bflow->name);
                                 ^~~~~

And a suggestion to just initialize bflow to NULL. This would however
would be ensuring a bad dereference. Instead, looking at the function we
rework things so that when CONFIG_EXPO is not enabled (and so, no UI) we
error early and would never reach this point in the code.  Simplify the
rest slightly as well while at this.

Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

Enable some messages that might provide hints, but only for
CMD_BOOTFLOW_FULL since otherwise the -l flag is not available.

Signed-off-by: Simon Glass <sjg@chromium.org>
Suggested-by: Tom Rini <trini@konsulko.com>

These flags actually relate to the iterator, not the bootflow struct
itself. Rename them.

Signed-off-by: Simon Glass <sjg@chromium.org>

It is sometimes useful to have one without the other, e.g. on a device
without a display, since at present the expo feature requires CONFIG_VIDEO
to be enabled.

Update the Makefile and bootflow command to support this, as well as the
EXPO dependency.

Signed-off-by: Simon Glass <sjg@chromium.org>

This function is not used outside tests. Drop it and rename
bootflow_scan_dev() since it is how we start a scan now.

Signed-off-by: Simon Glass <sjg@chromium.org>

We want to support scanning a single label, like 'mmc' or 'usb0'. Add
this feature by plumbing the label through to the iterator, setting a
flag to indicate that only siblings of the initial device should be used.

This means that scanning a bootdev by its name is not supported anymore.
That feature doesn't seem very useful in practice, so it is no great loss.

Add a test for bootdev_find_by_any() while we are here.

Signed-off-by: Simon Glass <sjg@chromium.org>

Add a flag to control whether hunters are used when scanning for
bootflows. Enable it by default and tidy up the flag comments a little.

Fow now this has no effect, until a future patch enables this feature.

Signed-off-by: Simon Glass <sjg@chromium.org>

These are associated with the ethernet boot device but do not match its
uclass name, so handle them as special cases.

Provide a way to pass flags through with the bootdev so that we know
how to process it. The flags are checked by the bootmeths, to ensure that
only the selected bootmeth is used.

While these both use the network device, they work quite differently. It
is common to run only one of these, or to run PXE before DHCP. Provide
bootflow flags to control which methods are used. Check these in the two
bootmeths so that only the chosen one is used.

Signed-off-by: Simon Glass <sjg@chromium.org>

Some bootmeths provide a way to load a device tree as well as the base
OS image. Add a way to store this in the bootflow. Update the
'bootflow info' command to show this information.

Note that the device tree is not allocated, but instead is stored at
an address provided by an environment variable. This may need to be
adjusted at some point, but for now it works well and fits in with the
existing distro-boot scripts.

Signed-off-by: Simon Glass <sjg@chromium.org>

Create an expo to handle the boot menu. For now this is quite simple, with
just a header, some menu items and a pointer to show the current one.

Signed-off-by: Simon Glass <sjg@chromium.org>