Hi Laurent,
I agree with your comments and will update and repost my patch
during the upcoming holy days.
Matthias
> Hi Matthias,
>
> On Friday 19 December 2008 00:48:34 Matthias Fuchs wrote:
> > Hi,
> >
> > please see my patch for enabling the RS485 half-duplex control below.
> > Please note that I am using this on a PowerPC platform. So I needed to
> > add the ioctl to the PowerPC header. As Wolfgang stated, it is
> > already in the x86 header. I am not sure if I have to post the
> > modification on the powerpc header to the PowerPC list or if it will be
> > accepted here as well. .... But first I will have to see what you think
> > of this patch
> >
> > :-)
>
> You will have to submit ioctls.h modifications as a separate patch to the
> powerpc-dev mailing list.
>
> The patch looks good, a few comments below.
>
> > Matthias
> >
> >
> > Some Exar UARTs support a auto rs485 mode. In this mode
> > the UART's RTS# pin is activated during transmitting and
> > can be used to enable a rs485 line driver. This has nothing
> > to do with attempts to do this by manually by asserting/
> > deasserting handshake lines.
> >
> > Signed-off-by: Matthias Fuchs <mfuchs@xxxxxxxx>
> > ---
> > arch/powerpc/include/asm/ioctls.h | 2 +
> > drivers/serial/8250.c | 59
> > +++++++++++++++++++++++++++++++++++++ 2 files changed, 61 insertions(+),
> > 0 deletions(-)
> >
> > diff --git a/arch/powerpc/include/asm/ioctls.h
> > b/arch/powerpc/include/asm/ioctls.h index 279a622..1842186 100644
> > --- a/arch/powerpc/include/asm/ioctls.h
> > +++ b/arch/powerpc/include/asm/ioctls.h
> > @@ -89,6 +89,8 @@
> > #define TIOCSBRK 0x5427 /* BSD compatibility */
> > #define TIOCCBRK 0x5428 /* BSD compatibility */
> > #define TIOCGSID 0x5429 /* Return the session ID of FD */
> > +#define TIOCGRS485 0x542e
> > +#define TIOCSRS485 0x542f
> > #define TIOCGPTN _IOR('T',0x30, unsigned int) /* Get Pty Number (of
> > pty-mux device) */ #define TIOCSPTLCK _IOW('T',0x31, int) /* Lock/unlock
> > Pty */
> >
> > diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c
> > index 303272a..e6df50f 100644
> > --- a/drivers/serial/8250.c
> > +++ b/drivers/serial/8250.c
> > @@ -2511,6 +2511,64 @@ serial8250_type(struct uart_port *port)
> > return uart_config[type].name;
> > }
> >
> > +static int
> > +serial8250_ioctl_port(struct uart_port *port, unsigned int cmd, unsigned
> > long arg) +{
> > + struct uart_8250_port *up = (struct uart_8250_port *)port;
> > +
> > + switch (cmd) {
> > + case TIOCSRS485:
> > + {
> > + struct serial_rs485 rs485ctrl;
> > + unsigned char fctr;
> > +
> > + if (port->type != PORT_16850)
> > + return -ENODEV;
>
> According to the ioctl manpage, -ENOTTY might be better:
>
> "ENOTTY The specified request does not apply to the kind of object that the
> descriptor d references."
>
> > + if (copy_from_user(&rs485ctrl,
> > + (struct serial_rs485 *)arg,
> > + sizeof(rs485ctrl)))
> > + return -EFAULT;
> > +
> > + serial_outp(up, UART_LCR, 0xbf);
> > + fctr = serial_inp(up, UART_FCTR);
> > + if (rs485ctrl.flags & SER_RS485_ENABLED)
> > + fctr |= 0x08;
> > + else
> > + fctr &= ~0x08;
> > + serial_outp(up, UART_FCTR, fctr);
> > + serial_outp(up, UART_LCR, 0);
>
> Doesn't this require locking ? serial8250_break_ctl and
> serial8250_set_termios both take the port.lock spinlock to prevent races
> from messing up with UART_LCR.
>
> > + return 0;
> > + }
> > +
> > + case TIOCGRS485:
> > + {
> > + struct serial_rs485 rs485ctrl;
> > +
> > + if (port->type != PORT_16850)
> > + return -ENODEV;
>
> What about setting rs485ctrl.flags to 0 and returning with success when
> RS485 auto direction control is not supported by the hardware ? I'm not
> sure if the preferred semantic for get requests on unsupported features is
> to return an error or return a 'feature disabled' value.
>
> > + serial_outp(up, UART_LCR, 0xbf);
> > + if (serial_inp(up, UART_FCTR) & 0x08)
> > + rs485ctrl.flags = SER_RS485_ENABLED;
> > + else
> > + rs485ctrl.flags = 0;
> > + serial_outp(up, UART_LCR, 0);
>
> Ditto, doesn't this require locking ?
>
> > +
> > + if (copy_to_user((struct serial_rs485 *)arg,
> > + &rs485ctrl,
> > + sizeof(rs485ctrl)))
> > + return -EFAULT;
> > + return 0;
> > + }
> > +
> > + default:
> > + return -ENOIOCTLCMD;
> > + }
> > +
> > + return 0;
> > +}
> > +
> > static struct uart_ops serial8250_pops = {
> > .tx_empty = serial8250_tx_empty,
> > .set_mctrl = serial8250_set_mctrl,
> > @@ -2529,6 +2587,7 @@ static struct uart_ops serial8250_pops = {
> > .request_port = serial8250_request_port,
> > .config_port = serial8250_config_port,
> > .verify_port = serial8250_verify_port,
> > + .ioctl = serial8250_ioctl_port,
> > #ifdef CONFIG_CONSOLE_POLL
> > .poll_get_char = serial8250_get_poll_char,
> > .poll_put_char = serial8250_put_poll_char,
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