[PATCH v6 1/3] tty/serial: Add GPIOLIB helpers for controlling modem lines

[Richard Genoud]

2014-04-22 15:08 GMT+02:00 Yegor Yefremov <yegor_sub1 at visionsystems.de>:
> On 10.03.2014 17:45, Richard Genoud wrote:
>> This patch add some helpers to control modem lines (CTS/RTS/DSR...) via
>> GPIO.
>> This will be useful for many boards which have a serial controller that
>> only handle CTS/RTS pins (or even just RX/TX).
>>
>> Signed-off-by: Richard Genoud <richard.genoud at gmail.com>
>
> ....
>
>> +
>> +struct mctrl_gpios {
>> +     struct gpio_desc *gpio[UART_GPIO_MAX];
>> +};
>> +
>> +static const struct {
>> +     const char *name;
>> +     unsigned int mctrl;
>> +     bool dir_out;
>> +} mctrl_gpios_desc[UART_GPIO_MAX] = {
>> +     { "cts", TIOCM_CTS, false, },
>> +     { "dsr", TIOCM_DSR, false, },
>> +     { "dcd", TIOCM_CD, false, },
>> +     { "rng", TIOCM_RNG, false, },
>> +     { "rts", TIOCM_RTS, true, },
>> +     { "dtr", TIOCM_DTR, true, },
>> +     { "out1", TIOCM_OUT1, true, },
>> +     { "out2", TIOCM_OUT2, true, },
>> +};
>> +
>> +void mctrl_gpio_set(struct mctrl_gpios *gpios, unsigned int mctrl)
>> +{
>> +     enum mctrl_gpio_idx i;
>> +
>> +     if (IS_ERR_OR_NULL(gpios))
>> +             return;
>> +
>> +     for (i = 0; i < UART_GPIO_MAX; i++)
>> +             if (!IS_ERR_OR_NULL(gpios->gpio[i]) &&
>> +                 mctrl_gpios_desc[i].dir_out)
>> +                     gpiod_set_value(gpios->gpio[i],
>> +                                     !!(mctrl & mctrl_gpios_desc[i].mctrl));
>> +}
>> +EXPORT_SYMBOL_GPL(mctrl_gpio_set);
>> +
>> +struct gpio_desc *mctrl_gpio_to_gpiod(struct mctrl_gpios *gpios,
>> +                                   enum mctrl_gpio_idx gidx)
>> +{
>> +     if (!IS_ERR_OR_NULL(gpios) && !IS_ERR_OR_NULL(gpios->gpio[gidx]))
>> +             return gpios->gpio[gidx];
>> +     else
>> +             return NULL;
>> +}
>> +EXPORT_SYMBOL_GPL(mctrl_gpio_to_gpiod);
>> +
>> +unsigned int mctrl_gpio_get(struct mctrl_gpios *gpios, unsigned int *mctrl)
>> +{
>> +     enum mctrl_gpio_idx i;
>> +
>> +     /*
>> +      * return it unchanged if the structure is not allocated
>> +      */
>> +     if (IS_ERR_OR_NULL(gpios))
>> +             return *mctrl;
>> +
>> +     for (i = 0; i < UART_GPIO_MAX; i++) {
>> +             if (!IS_ERR_OR_NULL(gpios->gpio[i]) &&
>> +                 !mctrl_gpios_desc[i].dir_out) {
>> +                     if (gpiod_get_value(gpios->gpio[i]))
>> +                             *mctrl |= mctrl_gpios_desc[i].mctrl;
>> +                     else
>> +                             *mctrl &= ~mctrl_gpios_desc[i].mctrl;
>> +             }
>> +     }
>> +
>> +     return *mctrl;
>> +}
>> +EXPORT_SYMBOL_GPL(mctrl_gpio_get);
>
> Should this routine be renamed to msr_gpio_get() or perhaps better to give all values (inputs and outputs)?
>
> I'm trying to port this approach to omap-serial to implement RS485 switching. I need to know if RTS is already on or not and set it accordingly.
>
> What would be the best solution for this task using this new API?
Sorry, but I don't really get what you're trying to do.
Could you explain a little bit more ?

Richard.