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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Character line display core support
*
* Copyright (C) 2016 Imagination Technologies
* Author: Paul Burton <paul.burton@mips.com>
*
* Copyright (C) 2021 Glider bv
*/
#include <generated/utsrelease.h>
#include <linux/device.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/sysfs.h>
#include <linux/timer.h>
#include "line-display.h"
/**
* linedisp_scroll() - scroll the display by a character
* @t: really a pointer to the private data structure
*
* Scroll the current message along the display by one character, rearming the
* timer if required.
*/
static void linedisp_scroll(struct timer_list *t)
{
struct linedisp *linedisp = from_timer(linedisp, t, timer);
unsigned int i, ch = linedisp->scroll_pos;
unsigned int num_chars = linedisp->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 < linedisp->message_len; i++, ch++)
linedisp->buf[i] = linedisp->message[ch];
/* wrap around to the start of the string */
ch = 0;
}
/* update the display */
linedisp->update(linedisp);
/* move on to the next character */
linedisp->scroll_pos++;
linedisp->scroll_pos %= linedisp->message_len;
/* rearm the timer */
if (linedisp->message_len > num_chars)
mod_timer(&linedisp->timer, jiffies + linedisp->scroll_rate);
}
/**
* linedisp_display() - set the message to be displayed
* @linedisp: pointer to the private data structure
* @msg: the message to display
* @count: length of msg, or -1
*
* Display a new message @msg on the display. @msg can be longer than the
* number of characters the display can display, in which case it will begin
* scrolling across the display.
*
* Return: 0 on success, -ENOMEM on memory allocation failure
*/
static int linedisp_display(struct linedisp *linedisp, const char *msg,
ssize_t count)
{
char *new_msg;
/* stop the scroll timer */
del_timer_sync(&linedisp->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 display */
kfree(linedisp->message);
linedisp->message = NULL;
linedisp->message_len = 0;
memset(linedisp->buf, ' ', linedisp->num_chars);
linedisp->update(linedisp);
return 0;
}
new_msg = kmemdup_nul(msg, count, GFP_KERNEL);
if (!new_msg)
return -ENOMEM;
kfree(linedisp->message);
linedisp->message = new_msg;
linedisp->message_len = count;
linedisp->scroll_pos = 0;
/* update the display */
linedisp_scroll(&linedisp->timer);
return 0;
}
/**
* message_show() - read message via sysfs
* @dev: the display device
* @attr: the display message attribute
* @buf: the buffer to read the message into
*
* Read the current message being displayed or scrolled across the 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 linedisp *linedisp = container_of(dev, struct linedisp, dev);
return sysfs_emit(buf, "%s\n", linedisp->message);
}
/**
* message_store() - write a new message via sysfs
* @dev: the display device
* @attr: the display 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 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 linedisp *linedisp = container_of(dev, struct linedisp, dev);
int err;
err = linedisp_display(linedisp, buf, count);
return err ?: count;
}
static DEVICE_ATTR_RW(message);
static struct attribute *linedisp_attrs[] = {
&dev_attr_message.attr,
NULL,
};
ATTRIBUTE_GROUPS(linedisp);
static const struct device_type linedisp_type = {
.groups = linedisp_groups,
};
/**
* linedisp_register - register a character line display
* @linedisp: pointer to character line display structure
* @parent: parent device
* @num_chars: the number of characters that can be displayed
* @buf: pointer to a buffer that can hold @num_chars characters
* @update: Function called to update the display. This must not sleep!
*
* Return: zero on success, else a negative error code.
*/
int linedisp_register(struct linedisp *linedisp, struct device *parent,
unsigned int num_chars, char *buf,
void (*update)(struct linedisp *linedisp))
{
static atomic_t linedisp_id = ATOMIC_INIT(-1);
int err;
memset(linedisp, 0, sizeof(*linedisp));
linedisp->dev.parent = parent;
linedisp->dev.type = &linedisp_type;
linedisp->update = update;
linedisp->buf = buf;
linedisp->num_chars = num_chars;
linedisp->scroll_rate = HZ / 2;
device_initialize(&linedisp->dev);
dev_set_name(&linedisp->dev, "linedisp.%lu",
(unsigned long)atomic_inc_return(&linedisp_id));
/* initialise a timer for scrolling the message */
timer_setup(&linedisp->timer, linedisp_scroll, 0);
err = device_add(&linedisp->dev);
if (err)
goto out_del_timer;
/* display a default message */
err = linedisp_display(linedisp, "Linux " UTS_RELEASE " ", -1);
if (err)
goto out_del_dev;
return 0;
out_del_dev:
device_del(&linedisp->dev);
out_del_timer:
del_timer_sync(&linedisp->timer);
put_device(&linedisp->dev);
return err;
}
EXPORT_SYMBOL_GPL(linedisp_register);
/**
* linedisp_unregister - unregister a character line display
* @linedisp: pointer to character line display structure registered previously
* with linedisp_register()
*/
void linedisp_unregister(struct linedisp *linedisp)
{
device_del(&linedisp->dev);
del_timer_sync(&linedisp->timer);
kfree(linedisp->message);
put_device(&linedisp->dev);
}
EXPORT_SYMBOL_GPL(linedisp_unregister);
MODULE_LICENSE("GPL");
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