drivers/auxdisplay/img-ascii-lcd.c - third_party/linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * Copyright (C) 2016 Imagination Technologies
  * Author: Paul Burton <paul.burton@mips.com>
  */

 #include <generated/utsrelease.h>
 #include <linux/kernel.h>
 #include <linux/io.h>
 #include <linux/mfd/syscon.h>
 #include <linux/module.h>
 #include <linux/of_address.h>
 #include <linux/of_platform.h>
 #include <linux/platform_device.h>
 #include <linux/regmap.h>
 #include <linux/slab.h>
 #include <linux/sysfs.h>

 struct img_ascii_lcd_ctx;

 /**
  * struct img_ascii_lcd_config - Configuration information about an LCD model
  * @num_chars: the number of characters the LCD can display
  * @external_regmap: true if registers are in a system controller, else false
  * @update: function called to update the LCD
  */
 struct img_ascii_lcd_config {
 	unsigned int num_chars;
 	bool external_regmap;
 	void (*update)(struct img_ascii_lcd_ctx *ctx);
 };

 /**
  * struct img_ascii_lcd_ctx - Private data structure
  * @pdev: the ASCII LCD platform device
  * @base: the base address of the LCD registers
  * @regmap: the regmap through which LCD registers are accessed
  * @offset: the offset within regmap to the start of the LCD registers
  * @cfg: pointer to the LCD model configuration
  * @message: the full message to display or scroll on the LCD
  * @message_len: the length of the @message string
  * @scroll_pos: index of the first character of @message currently displayed
  * @scroll_rate: scroll interval in jiffies
  * @timer: timer used to implement scrolling
  * @curr: the string currently displayed on the LCD
  */
 struct img_ascii_lcd_ctx {
 	struct platform_device *pdev;
 	union {
 		void __iomem *base;
 		struct regmap *regmap;
 	};
 	u32 offset;
 	const struct img_ascii_lcd_config *cfg;
 	char *message;
 	unsigned int message_len;
 	unsigned int scroll_pos;
 	unsigned int scroll_rate;
 	struct timer_list timer;
 	char curr[] __aligned(8);
 };

 /*
  * MIPS Boston development board
  */

 static void boston_update(struct img_ascii_lcd_ctx *ctx)
 {
 	ulong val;

 #if BITS_PER_LONG == 64
 	val = *((u64 *)&ctx->curr[0]);
 	__raw_writeq(val, ctx->base);
 #elif BITS_PER_LONG == 32
 	val = *((u32 *)&ctx->curr[0]);
 	__raw_writel(val, ctx->base);
 	val = *((u32 *)&ctx->curr[4]);
 	__raw_writel(val, ctx->base + 4);
 #else
 # error Not 32 or 64 bit
 #endif
 }

 static struct img_ascii_lcd_config boston_config = {
 	.num_chars = 8,
 	.update = boston_update,
 };

 /*
  * MIPS Malta development board
  */

 static void malta_update(struct img_ascii_lcd_ctx *ctx)
 {
 	unsigned int i;
 	int err = 0;

 	for (i = 0; i < ctx->cfg->num_chars; i++) {
 		err = regmap_write(ctx->regmap,
 				   ctx->offset + (i * 8), ctx->curr[i]);
 		if (err)
 			break;
 	}

 	if (unlikely(err))
 		pr_err_ratelimited("Failed to update LCD display: %d\n", err);
 }

 static struct img_ascii_lcd_config malta_config = {
 	.num_chars = 8,
 	.external_regmap = true,
 	.update = malta_update,
 };

 /*
  * MIPS SEAD3 development board
  */

 enum {
 	SEAD3_REG_LCD_CTRL		= 0x00,
 #define SEAD3_REG_LCD_CTRL_SETDRAM	BIT(7)
 	SEAD3_REG_LCD_DATA		= 0x08,
 	SEAD3_REG_CPLD_STATUS		= 0x10,
 #define SEAD3_REG_CPLD_STATUS_BUSY	BIT(0)
 	SEAD3_REG_CPLD_DATA		= 0x18,
 #define SEAD3_REG_CPLD_DATA_BUSY	BIT(7)
 };

 static int sead3_wait_sm_idle(struct img_ascii_lcd_ctx *ctx)
 {
 	unsigned int status;
 	int err;

 	do {
 		err = regmap_read(ctx->regmap,
 				  ctx->offset + SEAD3_REG_CPLD_STATUS,
 				  &status);
 		if (err)
 			return err;
 	} while (status & SEAD3_REG_CPLD_STATUS_BUSY);

 	return 0;

 }

 static int sead3_wait_lcd_idle(struct img_ascii_lcd_ctx *ctx)
 {
 	unsigned int cpld_data;
 	int err;

 	err = sead3_wait_sm_idle(ctx);
 	if (err)
 		return err;

 	do {
 		err = regmap_read(ctx->regmap,
 				  ctx->offset + SEAD3_REG_LCD_CTRL,
 				  &cpld_data);
 		if (err)
 			return err;

 		err = sead3_wait_sm_idle(ctx);
 		if (err)
 			return err;

 		err = regmap_read(ctx->regmap,
 				  ctx->offset + SEAD3_REG_CPLD_DATA,
 				  &cpld_data);
 		if (err)
 			return err;
 	} while (cpld_data & SEAD3_REG_CPLD_DATA_BUSY);

 	return 0;
 }

 static void sead3_update(struct img_ascii_lcd_ctx *ctx)
 {
 	unsigned int i;
 	int err = 0;

 	for (i = 0; i < ctx->cfg->num_chars; i++) {
 		err = sead3_wait_lcd_idle(ctx);
 		if (err)
 			break;

 		err = regmap_write(ctx->regmap,
 				   ctx->offset + SEAD3_REG_LCD_CTRL,
 				   SEAD3_REG_LCD_CTRL_SETDRAM | i);
 		if (err)
 			break;

 		err = sead3_wait_lcd_idle(ctx);
 		if (err)
 			break;

 		err = regmap_write(ctx->regmap,
 				   ctx->offset + SEAD3_REG_LCD_DATA,
 				   ctx->curr[i]);
 		if (err)
 			break;
 	}

 	if (unlikely(err))
 		pr_err_ratelimited("Failed to update LCD display: %d\n", err);
 }

 static struct img_ascii_lcd_config sead3_config = {
 	.num_chars = 16,
 	.external_regmap = true,
 	.update = sead3_update,
 };

 static const struct of_device_id img_ascii_lcd_matches[] = {
 	{ .compatible = "img,boston-lcd", .data = &boston_config },
 	{ .compatible = "mti,malta-lcd", .data = &malta_config },
 	{ .compatible = "mti,sead3-lcd", .data = &sead3_config },
 	{ /* sentinel */ }
 };
 MODULE_DEVICE_TABLE(of, img_ascii_lcd_matches);

 /**
  * img_ascii_lcd_scroll() - scroll the display by a character
  * @t: really a pointer to the private data structure
  *
  * Scroll the current message along the LCD by one character, rearming the
  * timer if required.
  */
 static void img_ascii_lcd_scroll(struct timer_list *t)
 {
 	struct img_ascii_lcd_ctx *ctx = from_timer(ctx, t, timer);
 	unsigned int i, ch = ctx->scroll_pos;
 	unsigned int num_chars = ctx->cfg->num_chars;

 	/* update the current message string */
 	for (i = 0; i < num_chars;) {
 		/* copy as many characters from the string as possible */
 		for (; i < num_chars && ch < ctx->message_len; i++, ch++)
 			ctx->curr[i] = ctx->message[ch];

 		/* wrap around to the start of the string */
 		ch = 0;
 	}

 	/* update the LCD */
 	ctx->cfg->update(ctx);

 	/* move on to the next character */
 	ctx->scroll_pos++;
 	ctx->scroll_pos %= ctx->message_len;

 	/* rearm the timer */
 	if (ctx->message_len > ctx->cfg->num_chars)
 		mod_timer(&ctx->timer, jiffies + ctx->scroll_rate);
 }

 /**
  * img_ascii_lcd_display() - set the message to be displayed
  * @ctx: pointer to the private data structure
  * @msg: the message to display
  * @count: length of msg, or -1
  *
  * Display a new message @msg on the LCD. @msg can be longer than the number of
  * characters the LCD can display, in which case it will begin scrolling across
  * the LCD display.
  *
  * Return: 0 on success, -ENOMEM on memory allocation failure
  */
 static int img_ascii_lcd_display(struct img_ascii_lcd_ctx *ctx,
 			     const char *msg, ssize_t count)
 {
 	char *new_msg;

 	/* stop the scroll timer */
 	del_timer_sync(&ctx->timer);

 	if (count == -1)
 		count = strlen(msg);

 	/* if the string ends with a newline, trim it */
 	if (msg[count - 1] == '\n')
 		count--;

 	if (!count) {
 		/* clear the LCD */
 		devm_kfree(&ctx->pdev->dev, ctx->message);
 		ctx->message = NULL;
 		ctx->message_len = 0;
 		memset(ctx->curr, ' ', ctx->cfg->num_chars);
 		ctx->cfg->update(ctx);
 		return 0;
 	}

 	new_msg = devm_kmalloc(&ctx->pdev->dev, count + 1, GFP_KERNEL);
 	if (!new_msg)
 		return -ENOMEM;

 	memcpy(new_msg, msg, count);
 	new_msg[count] = 0;

 	if (ctx->message)
 		devm_kfree(&ctx->pdev->dev, ctx->message);

 	ctx->message = new_msg;
 	ctx->message_len = count;
 	ctx->scroll_pos = 0;

 	/* update the LCD */
 	img_ascii_lcd_scroll(&ctx->timer);

 	return 0;
 }

 /**
  * message_show() - read message via sysfs
  * @dev: the LCD device
  * @attr: the LCD message attribute
  * @buf: the buffer to read the message into
  *
  * Read the current message being displayed or scrolled across the LCD display
  * into @buf, for reads from sysfs.
  *
  * Return: the number of characters written to @buf
  */
 static ssize_t message_show(struct device *dev, struct device_attribute *attr,
 			    char *buf)
 {
 	struct img_ascii_lcd_ctx *ctx = dev_get_drvdata(dev);

 	return sprintf(buf, "%s\n", ctx->message);
 }

 /**
  * message_store() - write a new message via sysfs
  * @dev: the LCD device
  * @attr: the LCD message attribute
  * @buf: the buffer containing the new message
  * @count: the size of the message in @buf
  *
  * Write a new message to display or scroll across the LCD display from sysfs.
  *
  * Return: the size of the message on success, else -ERRNO
  */
 static ssize_t message_store(struct device *dev, struct device_attribute *attr,
 			     const char *buf, size_t count)
 {
 	struct img_ascii_lcd_ctx *ctx = dev_get_drvdata(dev);
 	int err;

 	err = img_ascii_lcd_display(ctx, buf, count);
 	return err ?: count;
 }

 static DEVICE_ATTR_RW(message);

 /**
  * img_ascii_lcd_probe() - probe an LCD display device
  * @pdev: the LCD platform device
  *
  * Probe an LCD display device, ensuring that we have the required resources in
  * order to access the LCD & setting up private data as well as sysfs files.
  *
  * Return: 0 on success, else -ERRNO
  */
 static int img_ascii_lcd_probe(struct platform_device *pdev)
 {
 	const struct of_device_id *match;
 	const struct img_ascii_lcd_config *cfg;
 	struct img_ascii_lcd_ctx *ctx;
 	int err;

 	match = of_match_device(img_ascii_lcd_matches, &pdev->dev);
 	if (!match)
 		return -ENODEV;

 	cfg = match->data;
 	ctx = devm_kzalloc(&pdev->dev, sizeof(*ctx) + cfg->num_chars,
 			   GFP_KERNEL);
 	if (!ctx)
 		return -ENOMEM;

 	if (cfg->external_regmap) {
 		ctx->regmap = syscon_node_to_regmap(pdev->dev.parent->of_node);
 		if (IS_ERR(ctx->regmap))
 			return PTR_ERR(ctx->regmap);

 		if (of_property_read_u32(pdev->dev.of_node, "offset",
 					 &ctx->offset))
 			return -EINVAL;
 	} else {
 		ctx->base = devm_platform_ioremap_resource(pdev, 0);
 		if (IS_ERR(ctx->base))
 			return PTR_ERR(ctx->base);
 	}

 	ctx->pdev = pdev;
 	ctx->cfg = cfg;
 	ctx->message = NULL;
 	ctx->scroll_pos = 0;
 	ctx->scroll_rate = HZ / 2;

 	/* initialise a timer for scrolling the message */
 	timer_setup(&ctx->timer, img_ascii_lcd_scroll, 0);

 	platform_set_drvdata(pdev, ctx);

 	/* display a default message */
 	err = img_ascii_lcd_display(ctx, "Linux " UTS_RELEASE "       ", -1);
 	if (err)
 		goto out_del_timer;

 	err = device_create_file(&pdev->dev, &dev_attr_message);
 	if (err)
 		goto out_del_timer;

 	return 0;
 out_del_timer:
 	del_timer_sync(&ctx->timer);
 	return err;
 }

 /**
  * img_ascii_lcd_remove() - remove an LCD display device
  * @pdev: the LCD platform device
  *
  * Remove an LCD display device, freeing private resources & ensuring that the
  * driver stops using the LCD display registers.
  *
  * Return: 0
  */
 static int img_ascii_lcd_remove(struct platform_device *pdev)
 {
 	struct img_ascii_lcd_ctx *ctx = platform_get_drvdata(pdev);

 	device_remove_file(&pdev->dev, &dev_attr_message);
 	del_timer_sync(&ctx->timer);
 	return 0;
 }

 static struct platform_driver img_ascii_lcd_driver = {
 	.driver = {
 		.name		= "img-ascii-lcd",
 		.of_match_table	= img_ascii_lcd_matches,
 	},
 	.probe	= img_ascii_lcd_probe,
 	.remove	= img_ascii_lcd_remove,
 };
 module_platform_driver(img_ascii_lcd_driver);

 MODULE_DESCRIPTION("Imagination Technologies ASCII LCD Display");
 MODULE_AUTHOR("Paul Burton <paul.burton@mips.com>");
 MODULE_LICENSE("GPL");
	// SPDX-License-Identifier: GPL-2.0-or-later
	/*
	* Copyright (C) 2016 Imagination Technologies
	* Author: Paul Burton <paul.burton@mips.com>
	*/

	#include <generated/utsrelease.h>
	#include <linux/kernel.h>
	#include <linux/io.h>
	#include <linux/mfd/syscon.h>
	#include <linux/module.h>
	#include <linux/of_address.h>
	#include <linux/of_platform.h>
	#include <linux/platform_device.h>
	#include <linux/regmap.h>
	#include <linux/slab.h>
	#include <linux/sysfs.h>

	struct img_ascii_lcd_ctx;

	/**
	* struct img_ascii_lcd_config - Configuration information about an LCD model
	* @num_chars: the number of characters the LCD can display
	* @external_regmap: true if registers are in a system controller, else false
	* @update: function called to update the LCD
	*/
	struct img_ascii_lcd_config {
	unsigned int num_chars;
	bool external_regmap;
	void (update)(struct img_ascii_lcd_ctx ctx);
	};

	/**
	* struct img_ascii_lcd_ctx - Private data structure
	* @pdev: the ASCII LCD platform device
	* @base: the base address of the LCD registers
	* @regmap: the regmap through which LCD registers are accessed
	* @offset: the offset within regmap to the start of the LCD registers
	* @cfg: pointer to the LCD model configuration
	* @message: the full message to display or scroll on the LCD
	* @message_len: the length of the @message string
	* @scroll_pos: index of the first character of @message currently displayed
	* @scroll_rate: scroll interval in jiffies
	* @timer: timer used to implement scrolling
	* @curr: the string currently displayed on the LCD
	*/
	struct img_ascii_lcd_ctx {
	struct platform_device *pdev;
	union {
	void __iomem *base;
	struct regmap *regmap;
	};
	u32 offset;
	const struct img_ascii_lcd_config *cfg;
	char *message;
	unsigned int message_len;
	unsigned int scroll_pos;
	unsigned int scroll_rate;
	struct timer_list timer;
	char curr[] __aligned(8);
	};

	/*
	* MIPS Boston development board
	*/

	static void boston_update(struct img_ascii_lcd_ctx *ctx)
	{
	ulong val;

	#if BITS_PER_LONG == 64
	val = ((u64 )&ctx->curr[0]);
	__raw_writeq(val, ctx->base);
	#elif BITS_PER_LONG == 32
	val = ((u32 )&ctx->curr[0]);
	__raw_writel(val, ctx->base);
	val = ((u32 )&ctx->curr[4]);
	__raw_writel(val, ctx->base + 4);
	#else
	# error Not 32 or 64 bit
	#endif
	}

	static struct img_ascii_lcd_config boston_config = {
	.num_chars = 8,
	.update = boston_update,
	};

	/*
	* MIPS Malta development board
	*/

	static void malta_update(struct img_ascii_lcd_ctx *ctx)
	{
	unsigned int i;
	int err = 0;

	for (i = 0; i < ctx->cfg->num_chars; i++) {
	err = regmap_write(ctx->regmap,
	ctx->offset + (i * 8), ctx->curr[i]);
	if (err)
	break;
	}

	if (unlikely(err))
	pr_err_ratelimited("Failed to update LCD display: %d\n", err);
	}

	static struct img_ascii_lcd_config malta_config = {
	.num_chars = 8,
	.external_regmap = true,
	.update = malta_update,
	};

	/*
	* MIPS SEAD3 development board
	*/

	enum {
	SEAD3_REG_LCD_CTRL = 0x00,
	#define SEAD3_REG_LCD_CTRL_SETDRAM BIT(7)
	SEAD3_REG_LCD_DATA = 0x08,
	SEAD3_REG_CPLD_STATUS = 0x10,
	#define SEAD3_REG_CPLD_STATUS_BUSY BIT(0)
	SEAD3_REG_CPLD_DATA = 0x18,
	#define SEAD3_REG_CPLD_DATA_BUSY BIT(7)
	};

	static int sead3_wait_sm_idle(struct img_ascii_lcd_ctx *ctx)
	{
	unsigned int status;
	int err;

	do {
	err = regmap_read(ctx->regmap,
	ctx->offset + SEAD3_REG_CPLD_STATUS,
	&status);
	if (err)
	return err;
	} while (status & SEAD3_REG_CPLD_STATUS_BUSY);

	return 0;

	}

	static int sead3_wait_lcd_idle(struct img_ascii_lcd_ctx *ctx)
	{
	unsigned int cpld_data;
	int err;

	err = sead3_wait_sm_idle(ctx);
	if (err)
	return err;

	do {
	err = regmap_read(ctx->regmap,
	ctx->offset + SEAD3_REG_LCD_CTRL,
	&cpld_data);
	if (err)
	return err;

	err = sead3_wait_sm_idle(ctx);
	if (err)
	return err;

	err = regmap_read(ctx->regmap,
	ctx->offset + SEAD3_REG_CPLD_DATA,
	&cpld_data);
	if (err)
	return err;
	} while (cpld_data & SEAD3_REG_CPLD_DATA_BUSY);

	return 0;
	}

	static void sead3_update(struct img_ascii_lcd_ctx *ctx)
	{
	unsigned int i;
	int err = 0;

	for (i = 0; i < ctx->cfg->num_chars; i++) {
	err = sead3_wait_lcd_idle(ctx);
	if (err)
	break;

	err = regmap_write(ctx->regmap,
	ctx->offset + SEAD3_REG_LCD_CTRL,
	SEAD3_REG_LCD_CTRL_SETDRAM \| i);
	if (err)
	break;

	err = sead3_wait_lcd_idle(ctx);
	if (err)
	break;

	err = regmap_write(ctx->regmap,
	ctx->offset + SEAD3_REG_LCD_DATA,
	ctx->curr[i]);
	if (err)
	break;
	}

	if (unlikely(err))
	pr_err_ratelimited("Failed to update LCD display: %d\n", err);
	}

	static struct img_ascii_lcd_config sead3_config = {
	.num_chars = 16,
	.external_regmap = true,
	.update = sead3_update,
	};

	static const struct of_device_id img_ascii_lcd_matches[] = {
	{ .compatible = "img,boston-lcd", .data = &boston_config },
	{ .compatible = "mti,malta-lcd", .data = &malta_config },
	{ .compatible = "mti,sead3-lcd", .data = &sead3_config },
	{ /* sentinel */ }
	};
	MODULE_DEVICE_TABLE(of, img_ascii_lcd_matches);

	/**
	* img_ascii_lcd_scroll() - scroll the display by a character
	* @t: really a pointer to the private data structure
	*
	* Scroll the current message along the LCD by one character, rearming the
	* timer if required.
	*/
	static void img_ascii_lcd_scroll(struct timer_list *t)
	{
	struct img_ascii_lcd_ctx *ctx = from_timer(ctx, t, timer);
	unsigned int i, ch = ctx->scroll_pos;
	unsigned int num_chars = ctx->cfg->num_chars;

	/* update the current message string */
	for (i = 0; i < num_chars;) {
	/* copy as many characters from the string as possible */
	for (; i < num_chars && ch < ctx->message_len; i++, ch++)
	ctx->curr[i] = ctx->message[ch];

	/* wrap around to the start of the string */
	ch = 0;
	}

	/* update the LCD */
	ctx->cfg->update(ctx);

	/* move on to the next character */
	ctx->scroll_pos++;
	ctx->scroll_pos %= ctx->message_len;

	/* rearm the timer */
	if (ctx->message_len > ctx->cfg->num_chars)
	mod_timer(&ctx->timer, jiffies + ctx->scroll_rate);
	}

	/**
	* img_ascii_lcd_display() - set the message to be displayed
	* @ctx: pointer to the private data structure
	* @msg: the message to display
	* @count: length of msg, or -1
	*
	* Display a new message @msg on the LCD. @msg can be longer than the number of
	* characters the LCD can display, in which case it will begin scrolling across
	* the LCD display.
	*
	* Return: 0 on success, -ENOMEM on memory allocation failure
	*/
	static int img_ascii_lcd_display(struct img_ascii_lcd_ctx *ctx,
	const char *msg, ssize_t count)
	{
	char *new_msg;

	/* stop the scroll timer */
	del_timer_sync(&ctx->timer);

	if (count == -1)
	count = strlen(msg);

	/* if the string ends with a newline, trim it */
	if (msg[count - 1] == '\n')
	count--;

	if (!count) {
	/* clear the LCD */
	devm_kfree(&ctx->pdev->dev, ctx->message);
	ctx->message = NULL;
	ctx->message_len = 0;
	memset(ctx->curr, ' ', ctx->cfg->num_chars);
	ctx->cfg->update(ctx);
	return 0;
	}

	new_msg = devm_kmalloc(&ctx->pdev->dev, count + 1, GFP_KERNEL);
	if (!new_msg)
	return -ENOMEM;

	memcpy(new_msg, msg, count);
	new_msg[count] = 0;

	if (ctx->message)
	devm_kfree(&ctx->pdev->dev, ctx->message);

	ctx->message = new_msg;
	ctx->message_len = count;
	ctx->scroll_pos = 0;

	/* update the LCD */
	img_ascii_lcd_scroll(&ctx->timer);

	return 0;
	}

	/**
	* message_show() - read message via sysfs
	* @dev: the LCD device
	* @attr: the LCD message attribute
	* @buf: the buffer to read the message into
	*
	* Read the current message being displayed or scrolled across the LCD display
	* into @buf, for reads from sysfs.
	*
	* Return: the number of characters written to @buf
	*/
	static ssize_t message_show(struct device dev, struct device_attribute attr,
	char *buf)
	{
	struct img_ascii_lcd_ctx *ctx = dev_get_drvdata(dev);

	return sprintf(buf, "%s\n", ctx->message);
	}

	/**
	* message_store() - write a new message via sysfs
	* @dev: the LCD device
	* @attr: the LCD message attribute
	* @buf: the buffer containing the new message
	* @count: the size of the message in @buf
	*
	* Write a new message to display or scroll across the LCD display from sysfs.
	*
	* Return: the size of the message on success, else -ERRNO
	*/
	static ssize_t message_store(struct device dev, struct device_attribute attr,
	const char *buf, size_t count)
	{
	struct img_ascii_lcd_ctx *ctx = dev_get_drvdata(dev);
	int err;

	err = img_ascii_lcd_display(ctx, buf, count);
	return err ?: count;
	}

	static DEVICE_ATTR_RW(message);

	/**
	* img_ascii_lcd_probe() - probe an LCD display device
	* @pdev: the LCD platform device
	*
	* Probe an LCD display device, ensuring that we have the required resources in
	* order to access the LCD & setting up private data as well as sysfs files.
	*
	* Return: 0 on success, else -ERRNO
	*/
	static int img_ascii_lcd_probe(struct platform_device *pdev)
	{
	const struct of_device_id *match;
	const struct img_ascii_lcd_config *cfg;
	struct img_ascii_lcd_ctx *ctx;
	int err;

	match = of_match_device(img_ascii_lcd_matches, &pdev->dev);
	if (!match)
	return -ENODEV;

	cfg = match->data;
	ctx = devm_kzalloc(&pdev->dev, sizeof(*ctx) + cfg->num_chars,
	GFP_KERNEL);
	if (!ctx)
	return -ENOMEM;

	if (cfg->external_regmap) {
	ctx->regmap = syscon_node_to_regmap(pdev->dev.parent->of_node);
	if (IS_ERR(ctx->regmap))
	return PTR_ERR(ctx->regmap);

	if (of_property_read_u32(pdev->dev.of_node, "offset",
	&ctx->offset))
	return -EINVAL;
	} else {
	ctx->base = devm_platform_ioremap_resource(pdev, 0);
	if (IS_ERR(ctx->base))
	return PTR_ERR(ctx->base);
	}

	ctx->pdev = pdev;
	ctx->cfg = cfg;
	ctx->message = NULL;
	ctx->scroll_pos = 0;
	ctx->scroll_rate = HZ / 2;

	/* initialise a timer for scrolling the message */
	timer_setup(&ctx->timer, img_ascii_lcd_scroll, 0);

	platform_set_drvdata(pdev, ctx);

	/* display a default message */
	err = img_ascii_lcd_display(ctx, "Linux " UTS_RELEASE " ", -1);
	if (err)
	goto out_del_timer;

	err = device_create_file(&pdev->dev, &dev_attr_message);
	if (err)
	goto out_del_timer;

	return 0;
	out_del_timer:
	del_timer_sync(&ctx->timer);
	return err;
	}

	/**
	* img_ascii_lcd_remove() - remove an LCD display device
	* @pdev: the LCD platform device
	*
	* Remove an LCD display device, freeing private resources & ensuring that the
	* driver stops using the LCD display registers.
	*
	* Return: 0
	*/
	static int img_ascii_lcd_remove(struct platform_device *pdev)
	{
	struct img_ascii_lcd_ctx *ctx = platform_get_drvdata(pdev);

	device_remove_file(&pdev->dev, &dev_attr_message);
	del_timer_sync(&ctx->timer);
	return 0;
	}

	static struct platform_driver img_ascii_lcd_driver = {
	.driver = {
	.name = "img-ascii-lcd",
	.of_match_table = img_ascii_lcd_matches,
	},
	.probe = img_ascii_lcd_probe,
	.remove = img_ascii_lcd_remove,
	};
	module_platform_driver(img_ascii_lcd_driver);

	MODULE_DESCRIPTION("Imagination Technologies ASCII LCD Display");
	MODULE_AUTHOR("Paul Burton <paul.burton@mips.com>");
	MODULE_LICENSE("GPL");