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Re: [PATCH v8 3/3] tty: 8250_omap: Use software emulated RS485 direction control

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2016-02-11 23:19 GMT+03:00 Ильяс Гасанов <torso.nafi@gmail.com>:
> 2016-02-11 22:08 GMT+03:00 Matwey V. Kornilov <matwey@sai.msu.ru>:
>> Thanks for pointing out. serial8250_unregister_port should set
>> serial8250_ports[line].em485 to NULL in order to prevent unneeded
>> activation when this struct is reused.
>
> Then the allocated/initialized resources should be freed/released as well.

Sure, I've already sketched the patch, but to test it, I need some
time to build 8250_omap as a module and setup networking console and
kgdb over network.

>
>> You would be able to use serial8250_em485_register in omap8250_probe
>> on &up before serial8250_register_8250_port(&up) if
>> serial8250_register_8250_port could replicate em485 member state.
>> But there are alternatives in implementation.
>
> I'm considering adding the relevant code to the omap8250_startup and
> omap8250_shutdown callback functions. However the serial driver
> documentation claims that these don't have port->lock taken when
> invoked, only port_sem.
>
>> serial8250_register_8250_port may either copy pointer up->em485 to
>> uart->em485 or perform deep copy.
>
> Actually, "up" here in omap8250_probe is not a pointer but a struct
> variable on stack, so copying the pointer to it is out of question.
>

up->em485 is always pointer, however you are right, that
serial8250_em485_init stores pointer to up when the timers are inited.
More complex issue here that serial8250_em485_init need to set RTS to
proper state and probably can't do that before
serial8250_register_8250_port. So omap8250_probe should directly or
indirectly use serial8250_get_port(priv->line) after
serial8250_register_8250_port. As for me, possible solution could be
to add a wrapper:

int serial8250_em485_init_by_line(int line) {
    struct uart_8250_port *uart = &serial8250_ports[line];
    int ret;
    unsigned long flags;

    spin_lock_irqsave(&uart->port.lock, flags);
    ret = serial8250_em485_init(uart).
    spin_unlock_irqrestore(&uart->port.lock, flags);

    return ret;
}

>
> Regards,
> Ilyas G.
>



-- 
With best regards,
Matwey V. Kornilov.
Sternberg Astronomical Institute, Lomonosov Moscow State University, Russia
119991, Moscow, Universitetsky pr-k 13, +7 (495) 9392382

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Re: [PATCH v8 3/3] tty: 8250_omap: Use software emulated RS485  direction control Ильяс Гасанов   <torso.nafi@gmail.com> - 2016-02-11 17:50 +0100
  Re: [PATCH v8 3/3] tty: 8250_omap: Use software emulated RS485  direction control "Matwey V. Kornilov" <matwey@sai.msu.ru> - 2016-02-11 20:10 +0100
    Re: [PATCH v8 3/3] tty: 8250_omap: Use software emulated RS485  direction control Ильяс Гасанов   <torso.nafi@gmail.com> - 2016-02-11 21:30 +0100
      Re: [PATCH v8 3/3] tty: 8250_omap: Use software emulated RS485  direction control "Matwey V. Kornilov" <matwey@sai.msu.ru> - 2016-02-12 09:00 +0100
        Re: [PATCH v8 3/3] tty: 8250_omap: Use software emulated RS485  direction control Ильяс Гасанов   <torso.nafi@gmail.com> - 2016-02-12 10:40 +0100
          Re: [PATCH v8 3/3] tty: 8250_omap: Use software emulated RS485  direction control Ильяс Гасанов   <torso.nafi@gmail.com> - 2016-02-17 18:00 +0100
            Re: [PATCH v8 3/3] tty: 8250_omap: Use software emulated RS485  direction control Ильяс Гасанов   <torso.nafi@gmail.com> - 2016-02-18 08:20 +0100
              Re: [PATCH v8 3/3] tty: 8250_omap: Use software emulated RS485  direction control Ильяс Гасанов   <torso.nafi@gmail.com> - 2016-02-18 10:50 +0100
                Re: [PATCH v8 3/3] tty: 8250_omap: Use software emulated RS485  direction control Peter Hurley <peter@hurleysoftware.com> - 2016-02-18 18:00 +0100
                Re: [PATCH v8 3/3] tty: 8250_omap: Use software emulated RS485  direction control Ильяс Гасанов   <torso.nafi@gmail.com> - 2016-02-18 19:20 +0100

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