pstore: remove unused code ...

pstore_info->write() is unused, remove the code implementing it.

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

pstore: Only capture log messages ...

With this pstore only captures barebox log messages printed with pr_*
and dev_*, but no longer anything printed with printf and friends.

When capturing the barebox output with pstore only the log messages are
of interest, but not the ones printed with printf and certainly not
the things typed interactively on the command line. These are logged
currently because we register pstore as a barebox console. Instead, hook
into pr_puts which only outputs the barebox log messages.

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

pstore: Replace arguments for write() API ...

Similar to the pstore_info read() callback, there were too many arguments.
This switches to the new struct pstore_record pointer instead. This adds
"reason" and "part" to the record structure as well.

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

pstore: Replace arguments for read() API ...

The argument list for the pstore_read() interface is unwieldy. This changes
passes the new struct pstore_record instead. The erst backend was already
doing something similar internally.

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

pstore: Extract common arguments into structure ...

The read/mkfile pair pass the same arguments and should be cleared
between calls. Move to a structure and wipe it after every loop.

Signed-off-by: Kees Cook <keescook@chromium.org>
[p.zabel@pengutronix.de: ported to Barebox from Linux commit 9abdcccc3d5f]
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

fs: Add pstore filesystem ...

pstore is a persistent storage filesystem used for RAMOOPS. It is used
to store console logs, panics, ftrace and other information in case of a
crash/panic/oops/reboot.

pstore is implemented for barebox as a read-only filesystem at the
moment. It may be extended later on. The idea is to provide a way to
extract essential data from the last running kernel.

Most of the code is copied from the kernel. However this is only a
lightweight implementation without real write support yet.

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