[ +CC: Jiri, Alan, linux-serial ]
On Thu, Oct 16, 2014 at 02:09:29PM -0400, Peter Hurley wrote:
> On 10/16/2014 01:59 PM, Peter Hurley wrote:
> > Commit 90419cfcb5d9c889b10dc51363c56a4d394d670e,
> > "USB: kobil_sct: fix control requests without data stage", removed
> > the bogus data buffer arguments, but still allocate transfer
> > buffers which are not used.
> >
> > Cc: Johan Hovold <jhovold@xxxxxxxxx>
> > Signed-off-by: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx>
> > ---
> > drivers/usb/serial/kobil_sct.c | 15 ---------------
> > 1 file changed, 15 deletions(-)
> >
> > diff --git a/drivers/usb/serial/kobil_sct.c b/drivers/usb/serial/kobil_sct.c
> > index 078f9ed..3d2bd65 100644
> > --- a/drivers/usb/serial/kobil_sct.c
> > +++ b/drivers/usb/serial/kobil_sct.c
> > @@ -414,8 +414,6 @@ static int kobil_tiocmset(struct tty_struct *tty,
> > int result;
> > int dtr = 0;
> > int rts = 0;
> > - unsigned char *transfer_buffer;
> > - int transfer_buffer_length = 8;
> >
> > /* FIXME: locking ? */
> > priv = usb_get_serial_port_data(port);
> > @@ -425,11 +423,6 @@ static int kobil_tiocmset(struct tty_struct *tty,
> > return -EINVAL;
> > }
> >
> > - /* allocate memory for transfer buffer */
> > - transfer_buffer = kzalloc(transfer_buffer_length, GFP_KERNEL);
> > - if (!transfer_buffer)
> > - return -ENOMEM;
> > -
> > if (set & TIOCM_RTS)
> > rts = 1;
> > if (set & TIOCM_DTR)
> > @@ -469,7 +462,6 @@ static int kobil_tiocmset(struct tty_struct *tty,
> > KOBIL_TIMEOUT);
> > }
> > dev_dbg(dev, "%s - Send set_status_line URB returns: %i\n", __func__, result);
> > - kfree(transfer_buffer);
> > return (result < 0) ? result : 0;
> > }
> >
> > @@ -530,8 +522,6 @@ static int kobil_ioctl(struct tty_struct *tty,
> > {
> > struct usb_serial_port *port = tty->driver_data;
> > struct kobil_private *priv = usb_get_serial_port_data(port);
> > - unsigned char *transfer_buffer;
> > - int transfer_buffer_length = 8;
> > int result;
> >
> > if (priv->device_type == KOBIL_USBTWIN_PRODUCT_ID ||
> > @@ -541,10 +531,6 @@ static int kobil_ioctl(struct tty_struct *tty,
> >
> > switch (cmd) {
> > case TCFLSH:
> > - transfer_buffer = kmalloc(transfer_buffer_length, GFP_KERNEL);
> > - if (!transfer_buffer)
> > - return -ENOBUFS;
> > -
> > result = usb_control_msg(port->serial->dev,
> > usb_sndctrlpipe(port->serial->dev, 0),
> > SUSBCRequest_Misc,
> > @@ -559,7 +545,6 @@ static int kobil_ioctl(struct tty_struct *tty,
> > dev_dbg(&port->dev,
> > "%s - Send reset_all_queues (FLUSH) URB returns: %i\n",
> > __func__, result);
> > - kfree(transfer_buffer);
> > return (result < 0) ? -EIO: 0;
> ^^^
> Returning 0 is almost certainly wrong; no further processing for
> TCFLSH is performed.
Indeed.
> Only this driver returns 0 (of all the tty drivers in mainline).
>
> Returning -ENOIOCTLCMD allows further processing to continue;
> especially the line discipline's input flushing, if TCIFLUSH/TCIOFLUSH.
That doesn't seem like a very good idea, and only two *staging* drivers
try to play such games (i.e. pretending not to implement the ioctl) as
far as I can see.
The only non-staging tty driver which appears to implement TCFLSH,
ipwireless, calls tty_perform_flush directly to flush the ldisc buffers.
That doesn't seem right either.
Shouldn't this be fixed by removing TCFLSH from these tty drivers'
ioctl callbacks and implementing flush_buffer()?
The staging drivers also flush a device input buffer, which could be
done in a new callback if at all needed.
> Is it trying to avoid the tty_driver_flush_buffer() because it doesn't
> have an output buffer?
I don't think so. The author probably just assumed returning 0 for a
"handled" ioctl was the right thing to do.
I'll add flush_buffer support to usb-serial and fix up kobil_sct
meanwhile.
Thanks,
Johan
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