nv: add device parameter overwrites to completion list ...

nv variables in the form dev.<devname>.* can be used to make device
parameters persistent. Add these to the completion list to make setting
these variables more convenient.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

command: nv: rewrap help text lines ...

Just let the help text appear a bit more aligned.

Signed-off-by: Enrico Jorns <ejo@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

commands: nv: adjust command help ...

Help did not point out that -r option requires n arguments and did not
mention support for removing variables in help text.

Also introduce and consistently reuse 'NV' as abbreviation for 'non volatile'.

Signed-off-by: Enrico Jorns <ejo@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

commands: nv: assure error code will be returned when an error occurred ...

Due to iteration over possibly multiple variables, the return value of
an individual call to nvvar_remove() / nvvar_add() gets lost.

This will result in do_nv() returning success (0) if any variable
processing failed as long as processing of the last variable succeeded.

Processing will not be aborted on individual errors, such as the 'cp'
handles it for invalid files.

Signed-off-by: Enrico Jorns <ejo@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

commands: nv: call nvvar_print() only if no argument is given ...

Printing the nv variables (before performing any modification!) is useless
and irritating.

Signed-off-by: Enrico Jorns <ejo@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

commands: nv: fail with verbose message if invoked without args ...

Signed-off-by: Enrico Jorns <ejo@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

complete: Add completion for nv and globalvar commands ...

The 'nv' command is often used to create a nv variable
for an existing global variable, so add a command completion
function for this.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

nv: Allow to set/remove multiple variables with one command ...

It's convenient to set/remove multiple nv variables in one go. With
this patch we iterate over the remaining nonopts instead of expecting
exactly one nonopt.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

nv: Add option to explicitly save nv variables ...

We now have code to save the nv variables without saving the
rest of the environment. This gives us the possibility to explicitly
save the nv variables. This patch adds an option to the 'nv' command
for this.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Add support for non volatile variables ...

This adds (back) support for non volatile variables. Non volatile
variables are variables which are stored in the environment over
reboot. They are used in the same way as the global variables, but
with a 'nv' command and device. The variables are stored under
/env/nv/, one variable per file. Adding a nv variable automatically
adds a global variable with the same name. Changing a nv variable
also changes the same global variable, but not the other way round.
This allows for example to configure the username as:

nv user=sha; saveenv

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>