USB: serial: ftdi_sio: don't access latency timer on old chips

The latency timer was introduced with the FT232BM and FT245BM chips.  Do
not bother attempting to read or write it for older chip versions.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Johan Hovold <johan@kernel.org>

diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
index c540de15aad2c7d301543aef202b3560fb2f7399..72314734dfd0ea516a3174da1a9c860e2bef6267 100644 (file)
--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -1406,6 +1406,9 @@ static int write_latency_timer(struct usb_serial_port *port)
        int rv;
        int l = priv->latency;
 
+       if (priv->chip_type == SIO || priv->chip_type == FT8U232AM)
+               return -EINVAL;
+
        if (priv->flags & ASYNC_LOW_LATENCY)
                l = 1;
 
@@ -1429,6 +1432,9 @@ static int read_latency_timer(struct usb_serial_port *port)
        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;