305 lines
6.9 KiB
C
305 lines
6.9 KiB
C
// SPDX-License-Identifier: GPL-2.0+
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/*
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* HD44780 Character LCD driver for Linux
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*
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* Copyright (C) 2000-2008, Willy Tarreau <w@1wt.eu>
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* Copyright (C) 2016-2017 Glider bvba
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*/
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#include <linux/delay.h>
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#include <linux/gpio/consumer.h>
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#include <linux/module.h>
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#include <linux/mod_devicetable.h>
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#include <linux/platform_device.h>
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#include <linux/property.h>
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#include <linux/slab.h>
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#include <misc/charlcd.h>
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enum hd44780_pin {
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/* Order does matter due to writing to GPIO array subsets! */
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PIN_DATA0, /* Optional */
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PIN_DATA1, /* Optional */
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PIN_DATA2, /* Optional */
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PIN_DATA3, /* Optional */
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PIN_DATA4,
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PIN_DATA5,
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PIN_DATA6,
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PIN_DATA7,
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PIN_CTRL_RS,
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PIN_CTRL_RW, /* Optional */
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PIN_CTRL_E,
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PIN_CTRL_BL, /* Optional */
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PIN_NUM
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};
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struct hd44780 {
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struct gpio_desc *pins[PIN_NUM];
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};
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static void hd44780_backlight(struct charlcd *lcd, int on)
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{
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struct hd44780 *hd = lcd->drvdata;
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if (hd->pins[PIN_CTRL_BL])
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gpiod_set_value_cansleep(hd->pins[PIN_CTRL_BL], on);
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}
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static void hd44780_strobe_gpio(struct hd44780 *hd)
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{
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/* Maintain the data during 20 us before the strobe */
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udelay(20);
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gpiod_set_value_cansleep(hd->pins[PIN_CTRL_E], 1);
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/* Maintain the strobe during 40 us */
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udelay(40);
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gpiod_set_value_cansleep(hd->pins[PIN_CTRL_E], 0);
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}
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/* write to an LCD panel register in 8 bit GPIO mode */
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static void hd44780_write_gpio8(struct hd44780 *hd, u8 val, unsigned int rs)
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{
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DECLARE_BITMAP(values, 10); /* for DATA[0-7], RS, RW */
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unsigned int n;
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values[0] = val;
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__assign_bit(8, values, rs);
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n = hd->pins[PIN_CTRL_RW] ? 10 : 9;
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/* Present the data to the port */
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gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA0], NULL, values);
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hd44780_strobe_gpio(hd);
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}
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/* write to an LCD panel register in 4 bit GPIO mode */
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static void hd44780_write_gpio4(struct hd44780 *hd, u8 val, unsigned int rs)
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{
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DECLARE_BITMAP(values, 6); /* for DATA[4-7], RS, RW */
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unsigned int n;
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/* High nibble + RS, RW */
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values[0] = val >> 4;
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__assign_bit(4, values, rs);
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n = hd->pins[PIN_CTRL_RW] ? 6 : 5;
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/* Present the data to the port */
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gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA4], NULL, values);
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hd44780_strobe_gpio(hd);
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/* Low nibble */
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values[0] &= ~0x0fUL;
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values[0] |= val & 0x0f;
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/* Present the data to the port */
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gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA4], NULL, values);
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hd44780_strobe_gpio(hd);
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}
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/* Send a command to the LCD panel in 8 bit GPIO mode */
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static void hd44780_write_cmd_gpio8(struct charlcd *lcd, int cmd)
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{
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struct hd44780 *hd = lcd->drvdata;
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hd44780_write_gpio8(hd, cmd, 0);
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/* The shortest command takes at least 120 us */
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udelay(120);
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}
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/* Send data to the LCD panel in 8 bit GPIO mode */
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static void hd44780_write_data_gpio8(struct charlcd *lcd, int data)
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{
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struct hd44780 *hd = lcd->drvdata;
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hd44780_write_gpio8(hd, data, 1);
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/* The shortest data takes at least 45 us */
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udelay(45);
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}
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static const struct charlcd_ops hd44780_ops_gpio8 = {
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.write_cmd = hd44780_write_cmd_gpio8,
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.write_data = hd44780_write_data_gpio8,
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.backlight = hd44780_backlight,
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};
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/* Send a command to the LCD panel in 4 bit GPIO mode */
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static void hd44780_write_cmd_gpio4(struct charlcd *lcd, int cmd)
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{
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struct hd44780 *hd = lcd->drvdata;
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hd44780_write_gpio4(hd, cmd, 0);
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/* The shortest command takes at least 120 us */
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udelay(120);
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}
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/* Send 4-bits of a command to the LCD panel in raw 4 bit GPIO mode */
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static void hd44780_write_cmd_raw_gpio4(struct charlcd *lcd, int cmd)
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{
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DECLARE_BITMAP(values, 6); /* for DATA[4-7], RS, RW */
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struct hd44780 *hd = lcd->drvdata;
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unsigned int n;
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/* Command nibble + RS, RW */
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values[0] = cmd & 0x0f;
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n = hd->pins[PIN_CTRL_RW] ? 6 : 5;
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/* Present the data to the port */
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gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA4], NULL, values);
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hd44780_strobe_gpio(hd);
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}
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/* Send data to the LCD panel in 4 bit GPIO mode */
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static void hd44780_write_data_gpio4(struct charlcd *lcd, int data)
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{
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struct hd44780 *hd = lcd->drvdata;
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hd44780_write_gpio4(hd, data, 1);
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/* The shortest data takes at least 45 us */
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udelay(45);
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}
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static const struct charlcd_ops hd44780_ops_gpio4 = {
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.write_cmd = hd44780_write_cmd_gpio4,
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.write_cmd_raw4 = hd44780_write_cmd_raw_gpio4,
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.write_data = hd44780_write_data_gpio4,
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.backlight = hd44780_backlight,
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};
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static int hd44780_probe(struct platform_device *pdev)
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{
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struct device *dev = &pdev->dev;
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unsigned int i, base;
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struct charlcd *lcd;
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struct hd44780 *hd;
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int ifwidth, ret;
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/* Required pins */
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ifwidth = gpiod_count(dev, "data");
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if (ifwidth < 0)
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return ifwidth;
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switch (ifwidth) {
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case 4:
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base = PIN_DATA4;
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break;
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case 8:
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base = PIN_DATA0;
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break;
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default:
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return -EINVAL;
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}
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lcd = charlcd_alloc(sizeof(struct hd44780));
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if (!lcd)
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return -ENOMEM;
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hd = lcd->drvdata;
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for (i = 0; i < ifwidth; i++) {
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hd->pins[base + i] = devm_gpiod_get_index(dev, "data", i,
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GPIOD_OUT_LOW);
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if (IS_ERR(hd->pins[base + i])) {
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ret = PTR_ERR(hd->pins[base + i]);
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goto fail;
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}
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}
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hd->pins[PIN_CTRL_E] = devm_gpiod_get(dev, "enable", GPIOD_OUT_LOW);
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if (IS_ERR(hd->pins[PIN_CTRL_E])) {
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ret = PTR_ERR(hd->pins[PIN_CTRL_E]);
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goto fail;
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}
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hd->pins[PIN_CTRL_RS] = devm_gpiod_get(dev, "rs", GPIOD_OUT_HIGH);
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if (IS_ERR(hd->pins[PIN_CTRL_RS])) {
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ret = PTR_ERR(hd->pins[PIN_CTRL_RS]);
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goto fail;
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}
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/* Optional pins */
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hd->pins[PIN_CTRL_RW] = devm_gpiod_get_optional(dev, "rw",
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GPIOD_OUT_LOW);
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if (IS_ERR(hd->pins[PIN_CTRL_RW])) {
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ret = PTR_ERR(hd->pins[PIN_CTRL_RW]);
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goto fail;
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}
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hd->pins[PIN_CTRL_BL] = devm_gpiod_get_optional(dev, "backlight",
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GPIOD_OUT_LOW);
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if (IS_ERR(hd->pins[PIN_CTRL_BL])) {
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ret = PTR_ERR(hd->pins[PIN_CTRL_BL]);
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goto fail;
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}
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/* Required properties */
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ret = device_property_read_u32(dev, "display-height-chars",
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&lcd->height);
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if (ret)
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goto fail;
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ret = device_property_read_u32(dev, "display-width-chars", &lcd->width);
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if (ret)
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goto fail;
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/*
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* On displays with more than two rows, the internal buffer width is
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* usually equal to the display width
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*/
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if (lcd->height > 2)
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lcd->bwidth = lcd->width;
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/* Optional properties */
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device_property_read_u32(dev, "internal-buffer-width", &lcd->bwidth);
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lcd->ifwidth = ifwidth;
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lcd->ops = ifwidth == 8 ? &hd44780_ops_gpio8 : &hd44780_ops_gpio4;
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ret = charlcd_register(lcd);
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if (ret)
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goto fail;
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platform_set_drvdata(pdev, lcd);
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return 0;
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fail:
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kfree(lcd);
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return ret;
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}
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static int hd44780_remove(struct platform_device *pdev)
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{
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struct charlcd *lcd = platform_get_drvdata(pdev);
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charlcd_unregister(lcd);
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return 0;
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}
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static const struct of_device_id hd44780_of_match[] = {
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{ .compatible = "hit,hd44780" },
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{ /* sentinel */ }
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};
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MODULE_DEVICE_TABLE(of, hd44780_of_match);
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static struct platform_driver hd44780_driver = {
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.probe = hd44780_probe,
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.remove = hd44780_remove,
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.driver = {
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.name = "hd44780",
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.of_match_table = hd44780_of_match,
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},
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};
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module_platform_driver(hd44780_driver);
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MODULE_DESCRIPTION("HD44780 Character LCD driver");
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MODULE_AUTHOR("Geert Uytterhoeven <geert@linux-m68k.org>");
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MODULE_LICENSE("GPL");
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