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drivers/fet_proto.c: deal with spurious 0xff from Olimex adapter. 

The Olimex JTAG adapter occasionally emits an extra 0xff before sending
its reply to the C_INITIALIZE message. A small change to the FET packet
parser works around this.

Problem and original solution reported by Yingwei Li <ysulyw@gmail.com>.
This commit is contained in:
Daniel Beer 2015-05-11 13:01:49 +12:00
parent 3294192804
commit 56318beed1
1 changed files with 22 additions and 2 deletions
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24
drivers/fet_proto.c
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@ -204,13 +204,27 @@ too_short:
return -1; return -1;
} }
static void do_chomp_ff(struct fet_proto *dev)
{
int chomp_len = 0;
while ((chomp_len < dev->fet_len) && dev->fet_buf[chomp_len] == 0xff)
chomp_len++;
if (chomp_len)
memmove(dev->fet_buf, dev->fet_buf + chomp_len,
dev->fet_len - chomp_len);
dev->fet_len -= chomp_len;
}
/* Receive a packet from the FET. The usual format is: /* Receive a packet from the FET. The usual format is:
* <length (2 bytes)> <data> <checksum> * <length (2 bytes)> <data> <checksum>
* *
* The length is that of the data + checksum. Olimex JTAG adapters follow * The length is that of the data + checksum. Olimex JTAG adapters follow
* all packets with a trailing 0x7e byte, which must be discarded. * all packets with a trailing 0x7e byte, which must be discarded.
*/ */
static int recv_packet(struct fet_proto *dev) static int recv_packet(struct fet_proto *dev, int chomp_ff)
{ {
int pkt_extra = (dev->proto_flags & FET_PROTO_EXTRA_RECV) ? 3 : 2; int pkt_extra = (dev->proto_flags & FET_PROTO_EXTRA_RECV) ? 3 : 2;
int plen = LE_WORD(dev->fet_buf, 0); int plen = LE_WORD(dev->fet_buf, 0);
@ -237,6 +251,9 @@ static int recv_packet(struct fet_proto *dev)
if (len < 0) if (len < 0)
return -1; return -1;
dev->fet_len += len; dev->fet_len += len;
if (chomp_ff)
do_chomp_ff(dev);
} }
return -1; return -1;
@ -358,7 +375,10 @@ int fet_proto_xfer(struct fet_proto *dev,
data, datalen) < 0) data, datalen) < 0)
return -1; return -1;
if (recv_packet(dev) < 0) /* Olimex devices sometimes return a spurious 0xff before their
* response to C_INITIALIZE.
*/
if (recv_packet(dev, (command_code == 0x01)) < 0)
return -1; return -1;
if (dev->command_code != command_code) { if (dev->command_code != command_code) {