fs: let truncate take a loff_t argument ...

loff_t is the correct type for file sizes. Use it to allow to truncate
to sizes bigger than 32bit.

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

fs: devfs: Change .lseek callbacks to return 'int' ...

Returning requested offset from .lseek() callback doesn't really give
us any new information while bringing unnecessary
complications. Change all .lseek() types (both in struct struct
cdev_operations and in struct fs_driver_d) to return 'int' and adjust
the rest of the codebase accordingly.

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

fs: Update FILE position in lseek() ...

Instead on relying on driver callbacks to update 'pos' in FILE, do it
as a part of lseek() code. This allows us to drop a bit of repeating
code as well as making lseek() implementation consistent with write()
and read().

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

fs: smhfs: Fix return value of truncate() ...

Returning -ENOSYS as a result of truncate() breaks ability to write to
semihosting host's filesystem, so change the return value to 0. This
shouldn't cause any problems since all of the funcionlaity of
truncate() should is already handled by 'open' (via O_TRUNC) and
'write' (will automatically grow the file size when writing)
automatically

Unfortunately this was missed in original commit that introduced
semihosting

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

ARM: Add support for semihosting ...

Add semihosting API implementation and implement a filesystem driver
to access debugging host filesystem using it.

Tested on Freescale SabreSD board (i.MX6Q) using OpenOCD

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>