[Ftdi-usb-sio-devel] questions about ftdi_sio.c:update_mctrl()

[Leisner, M. <Mar...@xe...>]

I was looking at ftdi_sio in 2.6.10 -- and I noticed something I didn't
understand -- so I
looked in 2.6.18.2 and it was also there (but a little of the structure
changed).

Why do we kmalloc/kfree 1 byte...it seems it wouldn't be used in
usb_control_msg since
the size is 0...

So why don't we just do:
	NULL, 0
instead of
      buf, 0



static int update_mctrl(struct usb_serial_port *port, unsigned int set,
unsigned int clear)
{
        struct ftdi_private *priv =3D usb_get_serial_port_data(port);
        char *buf;
        unsigned urb_value;
        int rv;

        if (((set | clear) & (TIOCM_DTR | TIOCM_RTS)) =3D=3D 0) {
                dbg("%s - DTR|RTS not being set|cleared", __FUNCTION__);
                return 0;       /* no change */
        }

        buf =3D kmalloc(1, GFP_NOIO);
        if (!buf) {
                return -ENOMEM;
        }
....

        rv =3D usb_control_msg(port->serial->dev,
                               usb_sndctrlpipe(port->serial->dev, 0),
                               FTDI_SIO_SET_MODEM_CTRL_REQUEST,
                               FTDI_SIO_SET_MODEM_CTRL_REQUEST_TYPE,
                               urb_value, priv->interface,
                               buf, 0, WDR_TIMEOUT);

        kfree(buf);


marty