tty/serial: Add GPIOLIB helpers for controlling modem lines

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 110 insertions, 0 deletions

diff --git a/drivers/tty/serial/serial_mctrl_gpio.h b/drivers/tty/serial/serial_mctrl_gpio.h
new file mode 100644
index 000000000000..400ba0494a17
--- /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