1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Character line display core support
4 *
5 * Copyright (C) 2016 Imagination Technologies
6 * Author: Paul Burton <paul.burton@mips.com>
7 *
8 * Copyright (C) 2021 Glider bv
9 */
10
11#include <generated/utsrelease.h>
12
13#include <linux/container_of.h>
14#include <linux/device.h>
15#include <linux/export.h>
16#include <linux/idr.h>
17#include <linux/jiffies.h>
18#include <linux/kstrtox.h>
19#include <linux/module.h>
20#include <linux/slab.h>
21#include <linux/string.h>
22#include <linux/sysfs.h>
23#include <linux/timer.h>
24
25#include <linux/map_to_7segment.h>
26#include <linux/map_to_14segment.h>
27
28#include "line-display.h"
29
30#define DEFAULT_SCROLL_RATE	(HZ / 2)
31
32/**
33 * linedisp_scroll() - scroll the display by a character
34 * @t: really a pointer to the private data structure
35 *
36 * Scroll the current message along the display by one character, rearming the
37 * timer if required.
38 */
39static void linedisp_scroll(struct timer_list *t)
40{
41	struct linedisp *linedisp = from_timer(linedisp, t, timer);
42	unsigned int i, ch = linedisp->scroll_pos;
43	unsigned int num_chars = linedisp->num_chars;
44
45	/* update the current message string */
46	for (i = 0; i < num_chars;) {
47		/* copy as many characters from the string as possible */
48		for (; i < num_chars && ch < linedisp->message_len; i++, ch++)
49			linedisp->buf[i] = linedisp->message[ch];
50
51		/* wrap around to the start of the string */
52		ch = 0;
53	}
54
55	/* update the display */
56	linedisp->ops->update(linedisp);
57
58	/* move on to the next character */
59	linedisp->scroll_pos++;
60	linedisp->scroll_pos %= linedisp->message_len;
61
62	/* rearm the timer */
63	if (linedisp->message_len > num_chars && linedisp->scroll_rate)
64		mod_timer(&linedisp->timer, jiffies + linedisp->scroll_rate);
65}
66
67/**
68 * linedisp_display() - set the message to be displayed
69 * @linedisp: pointer to the private data structure
70 * @msg: the message to display
71 * @count: length of msg, or -1
72 *
73 * Display a new message @msg on the display. @msg can be longer than the
74 * number of characters the display can display, in which case it will begin
75 * scrolling across the display.
76 *
77 * Return: 0 on success, -ENOMEM on memory allocation failure
78 */
79static int linedisp_display(struct linedisp *linedisp, const char *msg,
80			    ssize_t count)
81{
82	char *new_msg;
83
84	/* stop the scroll timer */
85	del_timer_sync(&linedisp->timer);
86
87	if (count == -1)
88		count = strlen(msg);
89
90	/* if the string ends with a newline, trim it */
91	if (msg[count - 1] == '\n')
92		count--;
93
94	if (!count) {
95		/* Clear the display */
96		kfree(linedisp->message);
97		linedisp->message = NULL;
98		linedisp->message_len = 0;
99		memset(linedisp->buf, ' ', linedisp->num_chars);
100		linedisp->ops->update(linedisp);
101		return 0;
102	}
103
104	new_msg = kmemdup_nul(msg, count, GFP_KERNEL);
105	if (!new_msg)
106		return -ENOMEM;
107
108	kfree(linedisp->message);
109
110	linedisp->message = new_msg;
111	linedisp->message_len = count;
112	linedisp->scroll_pos = 0;
113
114	/* update the display */
115	linedisp_scroll(&linedisp->timer);
116
117	return 0;
118}
119
120/**
121 * message_show() - read message via sysfs
122 * @dev: the display device
123 * @attr: the display message attribute
124 * @buf: the buffer to read the message into
125 *
126 * Read the current message being displayed or scrolled across the display into
127 * @buf, for reads from sysfs.
128 *
129 * Return: the number of characters written to @buf
130 */
131static ssize_t message_show(struct device *dev, struct device_attribute *attr,
132			    char *buf)
133{
134	struct linedisp *linedisp = container_of(dev, struct linedisp, dev);
135
136	return sysfs_emit(buf, "%s\n", linedisp->message);
137}
138
139/**
140 * message_store() - write a new message via sysfs
141 * @dev: the display device
142 * @attr: the display message attribute
143 * @buf: the buffer containing the new message
144 * @count: the size of the message in @buf
145 *
146 * Write a new message to display or scroll across the display from sysfs.
147 *
148 * Return: the size of the message on success, else -ERRNO
149 */
150static ssize_t message_store(struct device *dev, struct device_attribute *attr,
151			     const char *buf, size_t count)
152{
153	struct linedisp *linedisp = container_of(dev, struct linedisp, dev);
154	int err;
155
156	err = linedisp_display(linedisp, buf, count);
157	return err ?: count;
158}
159
160static DEVICE_ATTR_RW(message);
161
162static ssize_t scroll_step_ms_show(struct device *dev,
163				   struct device_attribute *attr, char *buf)
164{
165	struct linedisp *linedisp = container_of(dev, struct linedisp, dev);
166
167	return sysfs_emit(buf, "%u\n", jiffies_to_msecs(linedisp->scroll_rate));
168}
169
170static ssize_t scroll_step_ms_store(struct device *dev,
171				    struct device_attribute *attr,
172				    const char *buf, size_t count)
173{
174	struct linedisp *linedisp = container_of(dev, struct linedisp, dev);
175	unsigned int ms;
176	int err;
177
178	err = kstrtouint(buf, 10, &ms);
179	if (err)
180		return err;
181
182	linedisp->scroll_rate = msecs_to_jiffies(ms);
183	if (linedisp->message && linedisp->message_len > linedisp->num_chars) {
184		del_timer_sync(&linedisp->timer);
185		if (linedisp->scroll_rate)
186			linedisp_scroll(&linedisp->timer);
187	}
188
189	return count;
190}
191
192static DEVICE_ATTR_RW(scroll_step_ms);
193
194static ssize_t map_seg_show(struct device *dev, struct device_attribute *attr, char *buf)
195{
196	struct linedisp *linedisp = container_of(dev, struct linedisp, dev);
197	struct linedisp_map *map = linedisp->map;
198
199	memcpy(buf, &map->map, map->size);
200	return map->size;
201}
202
203static ssize_t map_seg_store(struct device *dev, struct device_attribute *attr,
204			     const char *buf, size_t count)
205{
206	struct linedisp *linedisp = container_of(dev, struct linedisp, dev);
207	struct linedisp_map *map = linedisp->map;
208
209	if (count != map->size)
210		return -EINVAL;
211
212	memcpy(&map->map, buf, count);
213	return count;
214}
215
216static const SEG7_DEFAULT_MAP(initial_map_seg7);
217static DEVICE_ATTR(map_seg7, 0644, map_seg_show, map_seg_store);
218
219static const SEG14_DEFAULT_MAP(initial_map_seg14);
220static DEVICE_ATTR(map_seg14, 0644, map_seg_show, map_seg_store);
221
222static struct attribute *linedisp_attrs[] = {
223	&dev_attr_message.attr,
224	&dev_attr_scroll_step_ms.attr,
225	&dev_attr_map_seg7.attr,
226	&dev_attr_map_seg14.attr,
227	NULL
228};
229
230static umode_t linedisp_attr_is_visible(struct kobject *kobj, struct attribute *attr, int n)
231{
232	struct device *dev = kobj_to_dev(kobj);
233	struct linedisp *linedisp = container_of(dev, struct linedisp, dev);
234	struct linedisp_map *map = linedisp->map;
235	umode_t mode = attr->mode;
236
237	if (attr == &dev_attr_map_seg7.attr) {
238		if (!map)
239			return 0;
240		if (map->type != LINEDISP_MAP_SEG7)
241			return 0;
242	}
243
244	if (attr == &dev_attr_map_seg14.attr) {
245		if (!map)
246			return 0;
247		if (map->type != LINEDISP_MAP_SEG14)
248			return 0;
249	}
250
251	return mode;
252};
253
254static const struct attribute_group linedisp_group = {
255	.is_visible	= linedisp_attr_is_visible,
256	.attrs		= linedisp_attrs,
257};
258__ATTRIBUTE_GROUPS(linedisp);
259
260static DEFINE_IDA(linedisp_id);
261
262static void linedisp_release(struct device *dev)
263{
264	struct linedisp *linedisp = container_of(dev, struct linedisp, dev);
265
266	kfree(linedisp->map);
267	kfree(linedisp->message);
268	kfree(linedisp->buf);
269	ida_free(&linedisp_id, linedisp->id);
270}
271
272static const struct device_type linedisp_type = {
273	.groups	= linedisp_groups,
274	.release = linedisp_release,
275};
276
277static int linedisp_init_map(struct linedisp *linedisp)
278{
279	struct linedisp_map *map;
280	int err;
281
282	if (!linedisp->ops->get_map_type)
283		return 0;
284
285	err = linedisp->ops->get_map_type(linedisp);
286	if (err < 0)
287		return err;
288
289	map = kmalloc(sizeof(*map), GFP_KERNEL);
290	if (!map)
291		return -ENOMEM;
292
293	map->type = err;
294
295	/* assign initial mapping */
296	switch (map->type) {
297	case LINEDISP_MAP_SEG7:
298		map->map.seg7 = initial_map_seg7;
299		map->size = sizeof(map->map.seg7);
300		break;
301	case LINEDISP_MAP_SEG14:
302		map->map.seg14 = initial_map_seg14;
303		map->size = sizeof(map->map.seg14);
304		break;
305	default:
306		kfree(map);
307		return -EINVAL;
308	}
309
310	linedisp->map = map;
311
312	return 0;
313}
314
315/**
316 * linedisp_register - register a character line display
317 * @linedisp: pointer to character line display structure
318 * @parent: parent device
319 * @num_chars: the number of characters that can be displayed
320 * @ops: character line display operations
321 *
322 * Return: zero on success, else a negative error code.
323 */
324int linedisp_register(struct linedisp *linedisp, struct device *parent,
325		      unsigned int num_chars, const struct linedisp_ops *ops)
326{
327	int err;
328
329	memset(linedisp, 0, sizeof(*linedisp));
330	linedisp->dev.parent = parent;
331	linedisp->dev.type = &linedisp_type;
332	linedisp->ops = ops;
333	linedisp->num_chars = num_chars;
334	linedisp->scroll_rate = DEFAULT_SCROLL_RATE;
335
336	err = ida_alloc(&linedisp_id, GFP_KERNEL);
337	if (err < 0)
338		return err;
339	linedisp->id = err;
340
341	device_initialize(&linedisp->dev);
342	dev_set_name(&linedisp->dev, "linedisp.%u", linedisp->id);
343
344	err = -ENOMEM;
345	linedisp->buf = kzalloc(linedisp->num_chars, GFP_KERNEL);
346	if (!linedisp->buf)
347		goto out_put_device;
348
349	/* initialise a character mapping, if required */
350	err = linedisp_init_map(linedisp);
351	if (err)
352		goto out_put_device;
353
354	/* initialise a timer for scrolling the message */
355	timer_setup(&linedisp->timer, linedisp_scroll, 0);
356
357	err = device_add(&linedisp->dev);
358	if (err)
359		goto out_del_timer;
360
361	/* display a default message */
362	err = linedisp_display(linedisp, "Linux " UTS_RELEASE "       ", -1);
363	if (err)
364		goto out_del_dev;
365
366	return 0;
367
368out_del_dev:
369	device_del(&linedisp->dev);
370out_del_timer:
371	del_timer_sync(&linedisp->timer);
372out_put_device:
373	put_device(&linedisp->dev);
374	return err;
375}
376EXPORT_SYMBOL_NS_GPL(linedisp_register, LINEDISP);
377
378/**
379 * linedisp_unregister - unregister a character line display
380 * @linedisp: pointer to character line display structure registered previously
381 *	      with linedisp_register()
382 */
383void linedisp_unregister(struct linedisp *linedisp)
384{
385	device_del(&linedisp->dev);
386	del_timer_sync(&linedisp->timer);
387	put_device(&linedisp->dev);
388}
389EXPORT_SYMBOL_NS_GPL(linedisp_unregister, LINEDISP);
390
391MODULE_LICENSE("GPL");
392