Commit 3ac06b90 authored Jan 07, 2014 by Lars Poeschel Committed by Greg Kroah-Hartman Feb 07, 2014

tty: n_gsm: Fix for modems with brk in modem status control



3GPP TS 07.10 states in section 5.4.6.3.7:
"The length byte contains the value 2 or 3 ... depending on the break
signal." The break byte is optional and if it is sent, the length is
3. In fact the driver was not able to work with modems that send this
break byte in their modem status control message. If the modem just
sends the break byte if it is really set, then weird things might
happen.
The code for deconding the modem status to the internal linux
presentation in gsm_process_modem has already a big comment about
this 2 or 3 byte length thing and it is already able to decode the
brk, but the code calling the gsm_process_modem function in
gsm_control_modem does not encode it and hand it over the right way.
This patch fixes this.
Without this fix if the modem sends the brk byte in it's modem status
control message the driver will hang when opening a muxed channel.

Signed-off-by: Lars Poeschel <poeschel@lemonage.de>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 4fedd0bf

drivers/tty/n_gsm.c

+11 −0

Original line number	Diff line number	Diff line
		@@ -1090,6 +1090,7 @@ static void gsm_control_modem(struct gsm_mux gsm, u8 data, int clen)
		{
		unsigned int addr = 0;
		unsigned int modem = 0;
		unsigned int brk = 0;
		struct gsm_dlci *dlci;
		int len = clen;
		u8 *dp = data;
		@@ -1116,6 +1117,16 @@ static void gsm_control_modem(struct gsm_mux gsm, u8 data, int clen)
		if (len == 0)
		return;
		}
		len--;
		if (len > 0) {
		while (gsm_read_ea(&brk, *dp++) == 0) {
		len--;
		if (len == 0)
		return;
		}
		modem <<= 7;
		modem \|= (brk & 0x7f);
		}
		tty = tty_port_tty_get(&dlci->port);
		gsm_process_modem(tty, dlci, modem, clen);
		if (tty) {

Admin message