n_gsm: Fix support for legacy encoding
The mux supports several encoding schemes. Encoding 0 is a "not
recommended" mode still sometimes used. This has now been tested with
hardware that supports this mode, and found wanting.
Fix the FCS handling in this mode and correct the state machine.
Signed-off-by: Ken Mills <ken.k.mills@intel.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 04ef3ef..5256087 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -184,6 +184,9 @@
#define GSM_DATA 5
#define GSM_FCS 6
#define GSM_OVERRUN 7
+#define GSM_LEN0 8
+#define GSM_LEN1 9
+#define GSM_SSOF 10
unsigned int len;
unsigned int address;
unsigned int count;
@@ -191,6 +194,7 @@
int encoding;
u8 control;
u8 fcs;
+ u8 received_fcs;
u8 *txframe; /* TX framing buffer */
/* Methods for the receiver side */
@@ -1623,7 +1627,6 @@
kfree(dlci);
}
-
/*
* LAPBish link layer logic
*/
@@ -1648,6 +1651,8 @@
if ((gsm->control & ~PF) == UI)
gsm->fcs = gsm_fcs_add_block(gsm->fcs, gsm->buf, gsm->len);
+ /* generate final CRC with received FCS */
+ gsm->fcs = gsm_fcs_add(gsm->fcs, gsm->received_fcs);
if (gsm->fcs != GOOD_FCS) {
gsm->bad_fcs++;
if (debug & 4)
@@ -1746,6 +1751,8 @@
static void gsm0_receive(struct gsm_mux *gsm, unsigned char c)
{
+ unsigned int len;
+
switch (gsm->state) {
case GSM_SEARCH: /* SOF marker */
if (c == GSM0_SOF) {
@@ -1754,8 +1761,8 @@
gsm->len = 0;
gsm->fcs = INIT_FCS;
}
- break; /* Address EA */
- case GSM_ADDRESS:
+ break;
+ case GSM_ADDRESS: /* Address EA */
gsm->fcs = gsm_fcs_add(gsm->fcs, c);
if (gsm_read_ea(&gsm->address, c))
gsm->state = GSM_CONTROL;
@@ -1763,9 +1770,9 @@
case GSM_CONTROL: /* Control Byte */
gsm->fcs = gsm_fcs_add(gsm->fcs, c);
gsm->control = c;
- gsm->state = GSM_LEN;
+ gsm->state = GSM_LEN0;
break;
- case GSM_LEN: /* Length EA */
+ case GSM_LEN0: /* Length EA */
gsm->fcs = gsm_fcs_add(gsm->fcs, c);
if (gsm_read_ea(&gsm->len, c)) {
if (gsm->len > gsm->mru) {
@@ -1774,8 +1781,28 @@
break;
}
gsm->count = 0;
- gsm->state = GSM_DATA;
+ if (!gsm->len)
+ gsm->state = GSM_FCS;
+ else
+ gsm->state = GSM_DATA;
+ break;
}
+ gsm->state = GSM_LEN1;
+ break;
+ case GSM_LEN1:
+ gsm->fcs = gsm_fcs_add(gsm->fcs, c);
+ len = c;
+ gsm->len |= len << 7;
+ if (gsm->len > gsm->mru) {
+ gsm->bad_size++;
+ gsm->state = GSM_SEARCH;
+ break;
+ }
+ gsm->count = 0;
+ if (!gsm->len)
+ gsm->state = GSM_FCS;
+ else
+ gsm->state = GSM_DATA;
break;
case GSM_DATA: /* Data */
gsm->buf[gsm->count++] = c;
@@ -1783,16 +1810,25 @@
gsm->state = GSM_FCS;
break;
case GSM_FCS: /* FCS follows the packet */
- gsm->fcs = c;
+ gsm->received_fcs = c;
+ if (c == GSM0_SOF) {
+ gsm->state = GSM_SEARCH;
+ break;
+ }
gsm_queue(gsm);
- /* And then back for the next frame */
- gsm->state = GSM_SEARCH;
+ gsm->state = GSM_SSOF;
+ break;
+ case GSM_SSOF:
+ if (c == GSM0_SOF) {
+ gsm->state = GSM_SEARCH;
+ break;
+ }
break;
}
}
/**
- * gsm0_receive - perform processing for non-transparency
+ * gsm1_receive - perform processing for non-transparency
* @gsm: gsm data for this ldisc instance
* @c: character
*
@@ -2032,9 +2068,6 @@
}
EXPORT_SYMBOL_GPL(gsm_alloc_mux);
-
-
-
/**
* gsmld_output - write to link
* @gsm: our mux