tty: n_gsm: fix invalid gsmtty_write_room() result

gsmtty_write() does not prevent the user to use the full fifo size of 4096
bytes as allocated in gsm_dlci_alloc(). However, gsmtty_write_room() tries
to limit the return value by 'TX_SIZE' and returns a negative value if the
fifo has more than 'TX_SIZE' bytes stored. This is obviously wrong as
'TX_SIZE' is defined as 512.
Define 'TX_SIZE' to the fifo size and use it accordingly for allocation to
keep the current behavior. Return the correct remaining size of the fifo in
gsmtty_write_room() via kfifo_avail().

Fixes: e1eaea46bb40 ("tty: n_gsm line discipline")
Cc: [email protected]
Signed-off-by: Daniel Starke <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

0 files changed, 0 insertions, 0 deletions