Peter M. Groen / tty0tty

Less generic error code for write()

Allow tty0tty_write_room() to return ENOBUFS

See: https://github.com/torvalds/linux/commit/9f90a4ddef4e4d3aa4229f6b117d4e57231457b3
Closes: #36
Closes: #35
Signed-off-by: Matthew Bakhtiari <dev@mtbk.me>

Replaced the very generic EINVAL error code with ENOTCONN.
Because it is easy to trigger the error state of endpoint not connected.

Signed-off-by: Geert Stappers <stappers@stappers.it>

The very generic error code EINVAL, in function tty0tty_write,
replaced with more informative "No buffer space available"
return code ENOBUFS.

Signed-off-by: Geert Stappers <stappers@stappers.it>

Based on: http://dpdk.org/dev/patchwork/patch/22036/

Default value is 4

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