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![Geert Uytterhoeven](/assets/img/avatar_default.png)
If the message to display is longer than the number of characters that the display can show, the message will be scrolled. Currently the scroll rate is fixed, moving every 500 ms. Add support for changing the scroll rate through a "scroll_step_ms" device attribute in sysfs. Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org> Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
261 lines
6.8 KiB
C
261 lines
6.8 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* Character line display core support
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*
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* Copyright (C) 2016 Imagination Technologies
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* Author: Paul Burton <paul.burton@mips.com>
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*
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* Copyright (C) 2021 Glider bv
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*/
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#include <generated/utsrelease.h>
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#include <linux/device.h>
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#include <linux/module.h>
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#include <linux/slab.h>
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#include <linux/string.h>
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#include <linux/sysfs.h>
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#include <linux/timer.h>
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#include "line-display.h"
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#define DEFAULT_SCROLL_RATE (HZ / 2)
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/**
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* linedisp_scroll() - scroll the display by a character
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* @t: really a pointer to the private data structure
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*
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* Scroll the current message along the display by one character, rearming the
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* timer if required.
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*/
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static void linedisp_scroll(struct timer_list *t)
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{
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struct linedisp *linedisp = from_timer(linedisp, t, timer);
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unsigned int i, ch = linedisp->scroll_pos;
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unsigned int num_chars = linedisp->num_chars;
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/* update the current message string */
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for (i = 0; i < num_chars;) {
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/* copy as many characters from the string as possible */
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for (; i < num_chars && ch < linedisp->message_len; i++, ch++)
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linedisp->buf[i] = linedisp->message[ch];
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/* wrap around to the start of the string */
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ch = 0;
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}
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/* update the display */
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linedisp->update(linedisp);
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/* move on to the next character */
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linedisp->scroll_pos++;
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linedisp->scroll_pos %= linedisp->message_len;
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/* rearm the timer */
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if (linedisp->message_len > num_chars && linedisp->scroll_rate)
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mod_timer(&linedisp->timer, jiffies + linedisp->scroll_rate);
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}
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/**
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* linedisp_display() - set the message to be displayed
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* @linedisp: pointer to the private data structure
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* @msg: the message to display
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* @count: length of msg, or -1
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*
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* Display a new message @msg on the display. @msg can be longer than the
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* number of characters the display can display, in which case it will begin
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* scrolling across the display.
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*
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* Return: 0 on success, -ENOMEM on memory allocation failure
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*/
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static int linedisp_display(struct linedisp *linedisp, const char *msg,
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ssize_t count)
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{
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char *new_msg;
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/* stop the scroll timer */
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del_timer_sync(&linedisp->timer);
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if (count == -1)
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count = strlen(msg);
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/* if the string ends with a newline, trim it */
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if (msg[count - 1] == '\n')
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count--;
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if (!count) {
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/* Clear the display */
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kfree(linedisp->message);
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linedisp->message = NULL;
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linedisp->message_len = 0;
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memset(linedisp->buf, ' ', linedisp->num_chars);
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linedisp->update(linedisp);
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return 0;
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}
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new_msg = kmemdup_nul(msg, count, GFP_KERNEL);
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if (!new_msg)
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return -ENOMEM;
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kfree(linedisp->message);
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linedisp->message = new_msg;
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linedisp->message_len = count;
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linedisp->scroll_pos = 0;
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/* update the display */
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linedisp_scroll(&linedisp->timer);
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return 0;
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}
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/**
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* message_show() - read message via sysfs
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* @dev: the display device
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* @attr: the display message attribute
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* @buf: the buffer to read the message into
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*
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* Read the current message being displayed or scrolled across the display into
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* @buf, for reads from sysfs.
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*
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* Return: the number of characters written to @buf
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*/
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static ssize_t message_show(struct device *dev, struct device_attribute *attr,
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char *buf)
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{
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struct linedisp *linedisp = container_of(dev, struct linedisp, dev);
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return sysfs_emit(buf, "%s\n", linedisp->message);
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}
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/**
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* message_store() - write a new message via sysfs
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* @dev: the display device
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* @attr: the display message attribute
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* @buf: the buffer containing the new message
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* @count: the size of the message in @buf
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*
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* Write a new message to display or scroll across the display from sysfs.
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*
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* Return: the size of the message on success, else -ERRNO
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*/
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static ssize_t message_store(struct device *dev, struct device_attribute *attr,
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const char *buf, size_t count)
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{
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struct linedisp *linedisp = container_of(dev, struct linedisp, dev);
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int err;
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err = linedisp_display(linedisp, buf, count);
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return err ?: count;
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}
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static DEVICE_ATTR_RW(message);
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static ssize_t scroll_step_ms_show(struct device *dev,
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struct device_attribute *attr, char *buf)
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{
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struct linedisp *linedisp = container_of(dev, struct linedisp, dev);
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return sysfs_emit(buf, "%u\n", jiffies_to_msecs(linedisp->scroll_rate));
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}
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static ssize_t scroll_step_ms_store(struct device *dev,
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struct device_attribute *attr,
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const char *buf, size_t count)
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{
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struct linedisp *linedisp = container_of(dev, struct linedisp, dev);
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unsigned int ms;
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if (kstrtouint(buf, 10, &ms) != 0)
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return -EINVAL;
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linedisp->scroll_rate = msecs_to_jiffies(ms);
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if (linedisp->message && linedisp->message_len > linedisp->num_chars) {
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del_timer_sync(&linedisp->timer);
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if (linedisp->scroll_rate)
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linedisp_scroll(&linedisp->timer);
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}
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return count;
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}
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static DEVICE_ATTR_RW(scroll_step_ms);
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static struct attribute *linedisp_attrs[] = {
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&dev_attr_message.attr,
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&dev_attr_scroll_step_ms.attr,
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NULL,
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};
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ATTRIBUTE_GROUPS(linedisp);
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static const struct device_type linedisp_type = {
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.groups = linedisp_groups,
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};
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/**
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* linedisp_register - register a character line display
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* @linedisp: pointer to character line display structure
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* @parent: parent device
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* @num_chars: the number of characters that can be displayed
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* @buf: pointer to a buffer that can hold @num_chars characters
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* @update: Function called to update the display. This must not sleep!
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*
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* Return: zero on success, else a negative error code.
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*/
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int linedisp_register(struct linedisp *linedisp, struct device *parent,
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unsigned int num_chars, char *buf,
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void (*update)(struct linedisp *linedisp))
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{
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static atomic_t linedisp_id = ATOMIC_INIT(-1);
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int err;
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memset(linedisp, 0, sizeof(*linedisp));
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linedisp->dev.parent = parent;
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linedisp->dev.type = &linedisp_type;
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linedisp->update = update;
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linedisp->buf = buf;
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linedisp->num_chars = num_chars;
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linedisp->scroll_rate = DEFAULT_SCROLL_RATE;
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device_initialize(&linedisp->dev);
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dev_set_name(&linedisp->dev, "linedisp.%lu",
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(unsigned long)atomic_inc_return(&linedisp_id));
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/* initialise a timer for scrolling the message */
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timer_setup(&linedisp->timer, linedisp_scroll, 0);
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err = device_add(&linedisp->dev);
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if (err)
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goto out_del_timer;
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/* display a default message */
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err = linedisp_display(linedisp, "Linux " UTS_RELEASE " ", -1);
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if (err)
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goto out_del_dev;
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return 0;
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out_del_dev:
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device_del(&linedisp->dev);
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out_del_timer:
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del_timer_sync(&linedisp->timer);
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put_device(&linedisp->dev);
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return err;
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}
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EXPORT_SYMBOL_GPL(linedisp_register);
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/**
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* linedisp_unregister - unregister a character line display
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* @linedisp: pointer to character line display structure registered previously
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* with linedisp_register()
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*/
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void linedisp_unregister(struct linedisp *linedisp)
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{
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device_del(&linedisp->dev);
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del_timer_sync(&linedisp->timer);
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kfree(linedisp->message);
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put_device(&linedisp->dev);
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}
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EXPORT_SYMBOL_GPL(linedisp_unregister);
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MODULE_LICENSE("GPL");
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