diff mbox

[RESEND,3/5] tty/serial: Add GPIOLIB helpers for controlling modem lines

Message ID 1400005245-11943-4-git-send-email-richard.genoud@gmail.com (mailing list archive)
State New, archived
Headers show

Commit Message

Richard Genoud May 13, 2014, 6:20 p.m. UTC 
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@gmail.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 Documentation/serial/driver            |   25 ++++++
 drivers/tty/serial/Kconfig             |    3 +
 drivers/tty/serial/Makefile            |    3 +
 drivers/tty/serial/serial_mctrl_gpio.c |  143 ++++++++++++++++++++++++++++++++
 drivers/tty/serial/serial_mctrl_gpio.h |  110 ++++++++++++++++++++++++
 5 files changed, 284 insertions(+)
 create mode 100644 drivers/tty/serial/serial_mctrl_gpio.c
 create mode 100644 drivers/tty/serial/serial_mctrl_gpio.h

Comments

Yegor Yefremov May 20, 2014, 9:26 a.m. UTC | #1 
On 13.05.2014 20:20, 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@gmail.com>
> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Tested-by: Yegor Yefremov <yegorslists@googlemail.com>


> ---
>  Documentation/serial/driver            |   25 ++++++
>  drivers/tty/serial/Kconfig             |    3 +
>  drivers/tty/serial/Makefile            |    3 +
>  drivers/tty/serial/serial_mctrl_gpio.c |  143 ++++++++++++++++++++++++++++++++
>  drivers/tty/serial/serial_mctrl_gpio.h |  110 ++++++++++++++++++++++++
>  5 files changed, 284 insertions(+)
>  create mode 100644 drivers/tty/serial/serial_mctrl_gpio.c
>  create mode 100644 drivers/tty/serial/serial_mctrl_gpio.h
>
> diff --git a/Documentation/serial/driver b/Documentation/serial/driver
> index c3a7689..3bba1ae 100644
> --- a/Documentation/serial/driver
> +++ b/Documentation/serial/driver
> @@ -429,3 +429,28 @@ thus:
>  		struct uart_port	port;
>  		int			my_stuff;
>  	};
> +
> +Modem control lines via GPIO
> +----------------------------
> +
> +Some helpers are provided in order to set/get modem control lines via GPIO.
> +
> +mctrl_gpio_init(dev, idx):
> +	This will get the {cts,rts,...}-gpios from device tree if they are
> +	present and request them, set direction etc, and return an
> +	allocated structure. devm_* functions are used, so there's no need
> +	to call mctrl_gpio_free().
> +
> +mctrl_gpio_free(dev, gpios):
> +	This will free the requested gpios in mctrl_gpio_init().
> +	As devm_* function are used, there's generally no need to call
> +	this function.
> +
> +mctrl_gpio_to_gpiod(gpios, gidx)
> +	This returns the gpio structure associated to the modem line index.
> +
> +mctrl_gpio_set(gpios, mctrl):
> +	This will sets the gpios according to the mctrl state.
> +
> +mctrl_gpio_get(gpios, mctrl):
> +	This will update mctrl with the gpios values.
> diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
> index 5d9b01a..95afd31 100644
> --- a/drivers/tty/serial/Kconfig
> +++ b/drivers/tty/serial/Kconfig
> @@ -1510,4 +1510,7 @@ config SERIAL_ST_ASC_CONSOLE
>  
>  endmenu
>  
> +config SERIAL_MCTRL_GPIO
> +	tristate
> +
>  endif # TTY
> diff --git a/drivers/tty/serial/Makefile b/drivers/tty/serial/Makefile
> index 3680854..bcf31da 100644
> --- a/drivers/tty/serial/Makefile
> +++ b/drivers/tty/serial/Makefile
> @@ -87,3 +87,6 @@ obj-$(CONFIG_SERIAL_EFM32_UART) += efm32-uart.o
>  obj-$(CONFIG_SERIAL_ARC)	+= arc_uart.o
>  obj-$(CONFIG_SERIAL_RP2)	+= rp2.o
>  obj-$(CONFIG_SERIAL_FSL_LPUART)	+= fsl_lpuart.o
> +
> +# GPIOLIB helpers for modem control lines
> +obj-$(CONFIG_SERIAL_MCTRL_GPIO) += serial_mctrl_gpio.o
> diff --git a/drivers/tty/serial/serial_mctrl_gpio.c b/drivers/tty/serial/serial_mctrl_gpio.c
> new file mode 100644
> index 0000000..bf9560f
> --- /dev/null
> +++ b/drivers/tty/serial/serial_mctrl_gpio.c
> @@ -0,0 +1,143 @@
> +/*
> + * Helpers for controlling modem lines via GPIO
> + *
> + * Copyright (C) 2014 Paratronic S.A.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + */
> +
> +#include <linux/err.h>
> +#include <linux/device.h>
> +#include <linux/gpio/consumer.h>
> +#include <uapi/asm-generic/termios.h>
> +
> +#include "serial_mctrl_gpio.h"
> +
> +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);
> +
> +struct mctrl_gpios *mctrl_gpio_init(struct device *dev, unsigned int idx)
> +{
> +	struct mctrl_gpios *gpios;
> +	enum mctrl_gpio_idx i;
> +	int err;
> +
> +	gpios = devm_kzalloc(dev, sizeof(*gpios), GFP_KERNEL);
> +	if (!gpios)
> +		return ERR_PTR(-ENOMEM);
> +
> +	for (i = 0; i < UART_GPIO_MAX; i++) {
> +		gpios->gpio[i] = devm_gpiod_get_index(dev,
> +						      mctrl_gpios_desc[i].name,
> +						      idx);
> +
> +		/*
> +		 * The GPIOs are maybe not all filled,
> +		 * this is not an error.
> +		 */
> +		if (IS_ERR_OR_NULL(gpios->gpio[i]))
> +			continue;
> +
> +		if (mctrl_gpios_desc[i].dir_out)
> +			err = gpiod_direction_output(gpios->gpio[i], 0);
> +		else
> +			err = gpiod_direction_input(gpios->gpio[i]);
> +		if (err) {
> +			dev_dbg(dev, "Unable to set direction for %s GPIO",
> +				mctrl_gpios_desc[i].name);
> +			devm_gpiod_put(dev, gpios->gpio[i]);
> +			gpios->gpio[i] = NULL;
> +		}
> +	}
> +
> +	return gpios;
> +}
> +EXPORT_SYMBOL_GPL(mctrl_gpio_init);
> +
> +void mctrl_gpio_free(struct device *dev, struct mctrl_gpios *gpios)
> +{
> +	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]))
> +			devm_gpiod_put(dev, gpios->gpio[i]);
> +	devm_kfree(dev, gpios);
> +}
> +EXPORT_SYMBOL_GPL(mctrl_gpio_free);
> diff --git a/drivers/tty/serial/serial_mctrl_gpio.h b/drivers/tty/serial/serial_mctrl_gpio.h
> new file mode 100644
> index 0000000..400ba04
> --- /dev/null
> +++ b/drivers/tty/serial/serial_mctrl_gpio.h
> @@ -0,0 +1,110 @@
> +/*
> + * Helpers for controlling modem lines via GPIO
> + *
> + * Copyright (C) 2014 Paratronic S.A.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + */
> +
> +#ifndef __SERIAL_MCTRL_GPIO__
> +#define __SERIAL_MCTRL_GPIO__
> +
> +#include <linux/err.h>
> +#include <linux/device.h>
> +#include <linux/gpio/consumer.h>
> +
> +enum mctrl_gpio_idx {
> +	UART_GPIO_CTS,
> +	UART_GPIO_DSR,
> +	UART_GPIO_DCD,
> +	UART_GPIO_RNG,
> +	UART_GPIO_RI = UART_GPIO_RNG,
> +	UART_GPIO_RTS,
> +	UART_GPIO_DTR,
> +	UART_GPIO_OUT1,
> +	UART_GPIO_OUT2,
> +	UART_GPIO_MAX,
> +};
> +
> +/*
> + * Opaque descriptor for modem lines controlled by GPIOs
> + */
> +struct mctrl_gpios;
> +
> +#ifdef CONFIG_GPIOLIB
> +
> +/*
> + * Set state of the modem control output lines via GPIOs.
> + */
> +void mctrl_gpio_set(struct mctrl_gpios *gpios, unsigned int mctrl);
> +
> +/*
> + * Get state of the modem control output lines from GPIOs.
> + * The mctrl flags are updated and returned.
> + */
> +unsigned int mctrl_gpio_get(struct mctrl_gpios *gpios, unsigned int *mctrl);
> +
> +/*
> + * Returns the associated struct gpio_desc to the modem line gidx
> + */
> +struct gpio_desc *mctrl_gpio_to_gpiod(struct mctrl_gpios *gpios,
> +				      enum mctrl_gpio_idx gidx);
> +
> +/*
> + * Request and set direction of modem control lines GPIOs.
> + * devm_* functions are used, so there's no need to call mctrl_gpio_free().
> + * Returns a pointer to the allocated mctrl structure if ok, -ENOMEM on
> + * allocation error.
> + */
> +struct mctrl_gpios *mctrl_gpio_init(struct device *dev, unsigned int idx);
> +
> +/*
> + * Free the mctrl_gpios structure.
> + * Normally, this function will not be called, as the GPIOs will
> + * be disposed of by the resource management code.
> + */
> +void mctrl_gpio_free(struct device *dev, struct mctrl_gpios *gpios);
> +
> +#else /* GPIOLIB */
> +
> +static inline
> +void mctrl_gpio_set(struct mctrl_gpios *gpios, unsigned int mctrl)
> +{
> +}
> +
> +static inline
> +unsigned int mctrl_gpio_get(struct mctrl_gpios *gpios, unsigned int *mctrl)
> +{
> +	return *mctrl;
> +}
> +
> +static inline
> +struct gpio_desc *mctrl_gpio_to_gpiod(struct mctrl_gpios *gpios,
> +				      enum mctrl_gpio_idx gidx)
> +{
> +	return ERR_PTR(-ENOSYS);
> +}
> +
> +static inline
> +struct mctrl_gpios *mctrl_gpio_init(struct device *dev, unsigned int idx)
> +{
> +	return ERR_PTR(-ENOSYS);
> +}
> +
> +static inline
> +void mctrl_gpio_free(struct device *dev, struct mctrl_gpios *gpios)
> +{
> +}
> +
> +#endif /* GPIOLIB */
> +
> +#endif
Greg KH May 28, 2014, 7:45 p.m. UTC | #2 
On Tue, May 13, 2014 at 08:20:43PM +0200, 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@gmail.com>
> Tested-by: Yegor Yefremov <yegorslists@googlemail.com>
> ---
>  Documentation/serial/driver            |   25 ++++++
>  drivers/tty/serial/Kconfig             |    3 +
>  drivers/tty/serial/Makefile            |    3 +
>  drivers/tty/serial/serial_mctrl_gpio.c |  143 ++++++++++++++++++++++++++++++++
>  drivers/tty/serial/serial_mctrl_gpio.h |  110 ++++++++++++++++++++++++
>  5 files changed, 284 insertions(+)
>  create mode 100644 drivers/tty/serial/serial_mctrl_gpio.c
>  create mode 100644 drivers/tty/serial/serial_mctrl_gpio.h
> 
> diff --git a/Documentation/serial/driver b/Documentation/serial/driver
> index c3a7689..3bba1ae 100644
> --- a/Documentation/serial/driver
> +++ b/Documentation/serial/driver
> @@ -429,3 +429,28 @@ thus:
>  		struct uart_port	port;
>  		int			my_stuff;
>  	};
> +
> +Modem control lines via GPIO
> +----------------------------
> +
> +Some helpers are provided in order to set/get modem control lines via GPIO.
> +
> +mctrl_gpio_init(dev, idx):
> +	This will get the {cts,rts,...}-gpios from device tree if they are
> +	present and request them, set direction etc, and return an
> +	allocated structure. devm_* functions are used, so there's no need
> +	to call mctrl_gpio_free().
> +
> +mctrl_gpio_free(dev, gpios):
> +	This will free the requested gpios in mctrl_gpio_init().
> +	As devm_* function are used, there's generally no need to call
> +	this function.
> +
> +mctrl_gpio_to_gpiod(gpios, gidx)
> +	This returns the gpio structure associated to the modem line index.
> +
> +mctrl_gpio_set(gpios, mctrl):
> +	This will sets the gpios according to the mctrl state.
> +
> +mctrl_gpio_get(gpios, mctrl):
> +	This will update mctrl with the gpios values.
> diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
> index 5d9b01a..95afd31 100644
> --- a/drivers/tty/serial/Kconfig
> +++ b/drivers/tty/serial/Kconfig
> @@ -1510,4 +1510,7 @@ config SERIAL_ST_ASC_CONSOLE
>  
>  endmenu
>  
> +config SERIAL_MCTRL_GPIO
> +	tristate

Why is this added here?  Who is going to use it?

> +
>  endif # TTY
> diff --git a/drivers/tty/serial/Makefile b/drivers/tty/serial/Makefile
> index 3680854..bcf31da 100644
> --- a/drivers/tty/serial/Makefile
> +++ b/drivers/tty/serial/Makefile
> @@ -87,3 +87,6 @@ obj-$(CONFIG_SERIAL_EFM32_UART) += efm32-uart.o
>  obj-$(CONFIG_SERIAL_ARC)	+= arc_uart.o
>  obj-$(CONFIG_SERIAL_RP2)	+= rp2.o
>  obj-$(CONFIG_SERIAL_FSL_LPUART)	+= fsl_lpuart.o
> +
> +# GPIOLIB helpers for modem control lines
> +obj-$(CONFIG_SERIAL_MCTRL_GPIO) += serial_mctrl_gpio.o

This chunk doesn't apply anymore :(
Greg KH May 28, 2014, 7:47 p.m. UTC | #3 
On Wed, May 28, 2014 at 12:45:50PM -0700, Greg Kroah-Hartman wrote:
> On Tue, May 13, 2014 at 08:20:43PM +0200, 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@gmail.com>
> > Tested-by: Yegor Yefremov <yegorslists@googlemail.com>
> > ---
> >  Documentation/serial/driver            |   25 ++++++
> >  drivers/tty/serial/Kconfig             |    3 +
> >  drivers/tty/serial/Makefile            |    3 +
> >  drivers/tty/serial/serial_mctrl_gpio.c |  143 ++++++++++++++++++++++++++++++++
> >  drivers/tty/serial/serial_mctrl_gpio.h |  110 ++++++++++++++++++++++++
> >  5 files changed, 284 insertions(+)
> >  create mode 100644 drivers/tty/serial/serial_mctrl_gpio.c
> >  create mode 100644 drivers/tty/serial/serial_mctrl_gpio.h
> > 
> > diff --git a/Documentation/serial/driver b/Documentation/serial/driver
> > index c3a7689..3bba1ae 100644
> > --- a/Documentation/serial/driver
> > +++ b/Documentation/serial/driver
> > @@ -429,3 +429,28 @@ thus:
> >  		struct uart_port	port;
> >  		int			my_stuff;
> >  	};
> > +
> > +Modem control lines via GPIO
> > +----------------------------
> > +
> > +Some helpers are provided in order to set/get modem control lines via GPIO.
> > +
> > +mctrl_gpio_init(dev, idx):
> > +	This will get the {cts,rts,...}-gpios from device tree if they are
> > +	present and request them, set direction etc, and return an
> > +	allocated structure. devm_* functions are used, so there's no need
> > +	to call mctrl_gpio_free().
> > +
> > +mctrl_gpio_free(dev, gpios):
> > +	This will free the requested gpios in mctrl_gpio_init().
> > +	As devm_* function are used, there's generally no need to call
> > +	this function.
> > +
> > +mctrl_gpio_to_gpiod(gpios, gidx)
> > +	This returns the gpio structure associated to the modem line index.
> > +
> > +mctrl_gpio_set(gpios, mctrl):
> > +	This will sets the gpios according to the mctrl state.
> > +
> > +mctrl_gpio_get(gpios, mctrl):
> > +	This will update mctrl with the gpios values.
> > diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
> > index 5d9b01a..95afd31 100644
> > --- a/drivers/tty/serial/Kconfig
> > +++ b/drivers/tty/serial/Kconfig
> > @@ -1510,4 +1510,7 @@ config SERIAL_ST_ASC_CONSOLE
> >  
> >  endmenu
> >  
> > +config SERIAL_MCTRL_GPIO
> > +	tristate
> 
> Why is this added here?  Who is going to use it?

Ah, the next patch does, nevermind...
diff mbox

Patch

diff --git a/Documentation/serial/driver b/Documentation/serial/driver
index c3a7689..3bba1ae 100644
--- a/Documentation/serial/driver
+++ b/Documentation/serial/driver
@@ -429,3 +429,28 @@  thus:
 		struct uart_port	port;
 		int			my_stuff;
 	};
+
+Modem control lines via GPIO
+----------------------------
+
+Some helpers are provided in order to set/get modem control lines via GPIO.
+
+mctrl_gpio_init(dev, idx):
+	This will get the {cts,rts,...}-gpios from device tree if they are
+	present and request them, set direction etc, and return an
+	allocated structure. devm_* functions are used, so there's no need
+	to call mctrl_gpio_free().
+
+mctrl_gpio_free(dev, gpios):
+	This will free the requested gpios in mctrl_gpio_init().
+	As devm_* function are used, there's generally no need to call
+	this function.
+
+mctrl_gpio_to_gpiod(gpios, gidx)
+	This returns the gpio structure associated to the modem line index.
+
+mctrl_gpio_set(gpios, mctrl):
+	This will sets the gpios according to the mctrl state.
+
+mctrl_gpio_get(gpios, mctrl):
+	This will update mctrl with the gpios values.
diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index 5d9b01a..95afd31 100644
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -1510,4 +1510,7 @@  config SERIAL_ST_ASC_CONSOLE
 
 endmenu
 
+config SERIAL_MCTRL_GPIO
+	tristate
+
 endif # TTY
diff --git a/drivers/tty/serial/Makefile b/drivers/tty/serial/Makefile
index 3680854..bcf31da 100644
--- a/drivers/tty/serial/Makefile
+++ b/drivers/tty/serial/Makefile
@@ -87,3 +87,6 @@  obj-$(CONFIG_SERIAL_EFM32_UART) += efm32-uart.o
 obj-$(CONFIG_SERIAL_ARC)	+= arc_uart.o
 obj-$(CONFIG_SERIAL_RP2)	+= rp2.o
 obj-$(CONFIG_SERIAL_FSL_LPUART)	+= fsl_lpuart.o
+
+# GPIOLIB helpers for modem control lines
+obj-$(CONFIG_SERIAL_MCTRL_GPIO) += serial_mctrl_gpio.o
diff --git a/drivers/tty/serial/serial_mctrl_gpio.c b/drivers/tty/serial/serial_mctrl_gpio.c
new file mode 100644
index 0000000..bf9560f
--- /dev/null
+++ b/drivers/tty/serial/serial_mctrl_gpio.c
@@ -0,0 +1,143 @@ 
+/*
+ * Helpers for controlling modem lines via GPIO
+ *
+ * Copyright (C) 2014 Paratronic S.A.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include <linux/err.h>
+#include <linux/device.h>
+#include <linux/gpio/consumer.h>
+#include <uapi/asm-generic/termios.h>
+
+#include "serial_mctrl_gpio.h"
+
+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);
+
+struct mctrl_gpios *mctrl_gpio_init(struct device *dev, unsigned int idx)
+{
+	struct mctrl_gpios *gpios;
+	enum mctrl_gpio_idx i;
+	int err;
+
+	gpios = devm_kzalloc(dev, sizeof(*gpios), GFP_KERNEL);
+	if (!gpios)
+		return ERR_PTR(-ENOMEM);
+
+	for (i = 0; i < UART_GPIO_MAX; i++) {
+		gpios->gpio[i] = devm_gpiod_get_index(dev,
+						      mctrl_gpios_desc[i].name,
+						      idx);
+
+		/*
+		 * The GPIOs are maybe not all filled,
+		 * this is not an error.
+		 */
+		if (IS_ERR_OR_NULL(gpios->gpio[i]))
+			continue;
+
+		if (mctrl_gpios_desc[i].dir_out)
+			err = gpiod_direction_output(gpios->gpio[i], 0);
+		else
+			err = gpiod_direction_input(gpios->gpio[i]);
+		if (err) {
+			dev_dbg(dev, "Unable to set direction for %s GPIO",
+				mctrl_gpios_desc[i].name);
+			devm_gpiod_put(dev, gpios->gpio[i]);
+			gpios->gpio[i] = NULL;
+		}
+	}
+
+	return gpios;
+}
+EXPORT_SYMBOL_GPL(mctrl_gpio_init);
+
+void mctrl_gpio_free(struct device *dev, struct mctrl_gpios *gpios)
+{
+	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]))
+			devm_gpiod_put(dev, gpios->gpio[i]);
+	devm_kfree(dev, gpios);
+}
+EXPORT_SYMBOL_GPL(mctrl_gpio_free);
diff --git a/drivers/tty/serial/serial_mctrl_gpio.h b/drivers/tty/serial/serial_mctrl_gpio.h
new file mode 100644
index 0000000..400ba04
--- /dev/null
+++ b/drivers/tty/serial/serial_mctrl_gpio.h
@@ -0,0 +1,110 @@ 
+/*
+ * Helpers for controlling modem lines via GPIO
+ *
+ * Copyright (C) 2014 Paratronic S.A.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#ifndef __SERIAL_MCTRL_GPIO__
+#define __SERIAL_MCTRL_GPIO__
+
+#include <linux/err.h>
+#include <linux/device.h>
+#include <linux/gpio/consumer.h>
+
+enum mctrl_gpio_idx {
+	UART_GPIO_CTS,
+	UART_GPIO_DSR,
+	UART_GPIO_DCD,
+	UART_GPIO_RNG,
+	UART_GPIO_RI = UART_GPIO_RNG,
+	UART_GPIO_RTS,
+	UART_GPIO_DTR,
+	UART_GPIO_OUT1,
+	UART_GPIO_OUT2,
+	UART_GPIO_MAX,
+};
+
+/*
+ * Opaque descriptor for modem lines controlled by GPIOs
+ */
+struct mctrl_gpios;
+
+#ifdef CONFIG_GPIOLIB
+
+/*
+ * Set state of the modem control output lines via GPIOs.
+ */
+void mctrl_gpio_set(struct mctrl_gpios *gpios, unsigned int mctrl);
+
+/*
+ * Get state of the modem control output lines from GPIOs.
+ * The mctrl flags are updated and returned.
+ */
+unsigned int mctrl_gpio_get(struct mctrl_gpios *gpios, unsigned int *mctrl);
+
+/*
+ * Returns the associated struct gpio_desc to the modem line gidx
+ */
+struct gpio_desc *mctrl_gpio_to_gpiod(struct mctrl_gpios *gpios,
+				      enum mctrl_gpio_idx gidx);
+
+/*
+ * Request and set direction of modem control lines GPIOs.
+ * devm_* functions are used, so there's no need to call mctrl_gpio_free().
+ * Returns a pointer to the allocated mctrl structure if ok, -ENOMEM on
+ * allocation error.
+ */
+struct mctrl_gpios *mctrl_gpio_init(struct device *dev, unsigned int idx);
+
+/*
+ * Free the mctrl_gpios structure.
+ * Normally, this function will not be called, as the GPIOs will
+ * be disposed of by the resource management code.
+ */
+void mctrl_gpio_free(struct device *dev, struct mctrl_gpios *gpios);
+
+#else /* GPIOLIB */
+
+static inline
+void mctrl_gpio_set(struct mctrl_gpios *gpios, unsigned int mctrl)
+{
+}
+
+static inline
+unsigned int mctrl_gpio_get(struct mctrl_gpios *gpios, unsigned int *mctrl)
+{
+	return *mctrl;
+}
+
+static inline
+struct gpio_desc *mctrl_gpio_to_gpiod(struct mctrl_gpios *gpios,
+				      enum mctrl_gpio_idx gidx)
+{
+	return ERR_PTR(-ENOSYS);
+}
+
+static inline
+struct mctrl_gpios *mctrl_gpio_init(struct device *dev, unsigned int idx)
+{
+	return ERR_PTR(-ENOSYS);
+}
+
+static inline
+void mctrl_gpio_free(struct device *dev, struct mctrl_gpios *gpios)
+{
+}
+
+#endif /* GPIOLIB */
+
+#endif