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USB: serial: ftdi_sio: detect BM chip with iSerialNumber bug 

If a BM type chip has iSerialNumber set to 0 in its EEPROM, an incorrect
value is read from the bcdDevice field of the USB descriptor, making it
look like an AM type chip.  Attempt to correct this in
ftdi_determine_type() by attempting to read the latency timer for an AM
type chip if it has iSerialNumber set to 0.  If that succeeds, assume it
is a BM type chip.

Currently, read_latency_timer() bails out without reading the latency
timer for an AM type chip, so factor out the guts of
read_latency_timer() into a new function _read_latency_timer() that
attempts to read the latency timer regardless of chip type, and returns
either the latency timer value or a negative error number.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Johan Hovold <johan@kernel.org>
This commit is contained in:
Ian Abbott 2017-03-08 16:02:58 +00:00 committed by Johan Hovold
parent 2dea7cd728
commit 7e1e6ceda3
1 changed files with 33 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

41
drivers/usb/serial/ftdi_sio.c
View File

@ -1425,16 +1425,13 @@ static int write_latency_timer(struct usb_serial_port *port)
return rv;
}
static int read_latency_timer(struct usb_serial_port *port)
static int _read_latency_timer(struct usb_serial_port *port)
{
struct ftdi_private *priv = usb_get_serial_port_data(port);
struct usb_device *udev = port->serial->dev;
unsigned char *buf;
int rv;
if (priv->chip_type == SIO || priv->chip_type == FT8U232AM)
return -EINVAL;
buf = kmalloc(1, GFP_KERNEL);
if (!buf)
return -ENOMEM;
@ -1446,11 +1443,10 @@ static int read_latency_timer(struct usb_serial_port *port)
0, priv->interface,
buf, 1, WDR_TIMEOUT);
if (rv < 1) {
dev_err(&port->dev, "Unable to read latency timer: %i\n", rv);
if (rv >= 0)
rv = -EIO;
} else {
priv->latency = buf[0];
rv = buf[0];
}
kfree(buf);
@ -1458,6 +1454,25 @@ static int read_latency_timer(struct usb_serial_port *port)
return rv;
}
static int read_latency_timer(struct usb_serial_port *port)
{
struct ftdi_private *priv = usb_get_serial_port_data(port);
int rv;
if (priv->chip_type == SIO || priv->chip_type == FT8U232AM)
return -EINVAL;
rv = _read_latency_timer(port);
if (rv < 0) {
dev_err(&port->dev, "Unable to read latency timer: %i\n", rv);
return rv;
}
priv->latency = rv;
return 0;
}
static int get_serial_info(struct usb_serial_port *port,
struct serial_struct __user *retinfo)
{
@ -1609,9 +1624,19 @@ static void ftdi_determine_type(struct usb_serial_port *port)
priv->baud_base = 12000000 / 16;
} else if (version < 0x400) {
/* Assume it's an FT8U232AM (or FT8U245AM) */
/* (It might be a BM because of the iSerialNumber bug,
* but it will still work as an AM device.) */
priv->chip_type = FT8U232AM;
/*
* It might be a BM type because of the iSerialNumber bug.
* If iSerialNumber==0 and the latency timer is readable,
* assume it is BM type.
*/
if (udev->descriptor.iSerialNumber == 0 &&
_read_latency_timer(port) >= 0) {
dev_dbg(&port->dev,
"%s: has latency timer so not an AM type\n",
__func__);
priv->chip_type = FT232BM;
}
} else if (version < 0x600) {
/* Assume it's an FT232BM (or FT245BM) */
priv->chip_type = FT232BM;