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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/device.h> | |
14 | #include <linux/module.h> | |
15 | #include <linux/slab.h> | |
16 | #include <linux/string.h> | |
17 | #include <linux/sysfs.h> | |
18 | #include <linux/timer.h> | |
19 | ||
20 | #include "line-display.h" | |
21 | ||
d79141c3 GU |
22 | #define DEFAULT_SCROLL_RATE (HZ / 2) |
23 | ||
7e76aece GU |
24 | /** |
25 | * linedisp_scroll() - scroll the display by a character | |
26 | * @t: really a pointer to the private data structure | |
27 | * | |
28 | * Scroll the current message along the display by one character, rearming the | |
29 | * timer if required. | |
30 | */ | |
31 | static void linedisp_scroll(struct timer_list *t) | |
32 | { | |
33 | struct linedisp *linedisp = from_timer(linedisp, t, timer); | |
34 | unsigned int i, ch = linedisp->scroll_pos; | |
35 | unsigned int num_chars = linedisp->num_chars; | |
36 | ||
37 | /* update the current message string */ | |
38 | for (i = 0; i < num_chars;) { | |
39 | /* copy as many characters from the string as possible */ | |
40 | for (; i < num_chars && ch < linedisp->message_len; i++, ch++) | |
41 | linedisp->buf[i] = linedisp->message[ch]; | |
42 | ||
43 | /* wrap around to the start of the string */ | |
44 | ch = 0; | |
45 | } | |
46 | ||
47 | /* update the display */ | |
48 | linedisp->update(linedisp); | |
49 | ||
50 | /* move on to the next character */ | |
51 | linedisp->scroll_pos++; | |
52 | linedisp->scroll_pos %= linedisp->message_len; | |
53 | ||
54 | /* rearm the timer */ | |
d79141c3 | 55 | if (linedisp->message_len > num_chars && linedisp->scroll_rate) |
7e76aece GU |
56 | mod_timer(&linedisp->timer, jiffies + linedisp->scroll_rate); |
57 | } | |
58 | ||
59 | /** | |
60 | * linedisp_display() - set the message to be displayed | |
61 | * @linedisp: pointer to the private data structure | |
62 | * @msg: the message to display | |
63 | * @count: length of msg, or -1 | |
64 | * | |
65 | * Display a new message @msg on the display. @msg can be longer than the | |
66 | * number of characters the display can display, in which case it will begin | |
67 | * scrolling across the display. | |
68 | * | |
69 | * Return: 0 on success, -ENOMEM on memory allocation failure | |
70 | */ | |
71 | static int linedisp_display(struct linedisp *linedisp, const char *msg, | |
72 | ssize_t count) | |
73 | { | |
74 | char *new_msg; | |
75 | ||
76 | /* stop the scroll timer */ | |
77 | del_timer_sync(&linedisp->timer); | |
78 | ||
79 | if (count == -1) | |
80 | count = strlen(msg); | |
81 | ||
82 | /* if the string ends with a newline, trim it */ | |
83 | if (msg[count - 1] == '\n') | |
84 | count--; | |
85 | ||
86 | if (!count) { | |
87 | /* Clear the display */ | |
88 | kfree(linedisp->message); | |
89 | linedisp->message = NULL; | |
90 | linedisp->message_len = 0; | |
91 | memset(linedisp->buf, ' ', linedisp->num_chars); | |
92 | linedisp->update(linedisp); | |
93 | return 0; | |
94 | } | |
95 | ||
364f2c39 | 96 | new_msg = kmemdup_nul(msg, count, GFP_KERNEL); |
7e76aece GU |
97 | if (!new_msg) |
98 | return -ENOMEM; | |
99 | ||
7e76aece GU |
100 | kfree(linedisp->message); |
101 | ||
102 | linedisp->message = new_msg; | |
103 | linedisp->message_len = count; | |
104 | linedisp->scroll_pos = 0; | |
105 | ||
106 | /* update the display */ | |
107 | linedisp_scroll(&linedisp->timer); | |
108 | ||
109 | return 0; | |
110 | } | |
111 | ||
112 | /** | |
113 | * message_show() - read message via sysfs | |
114 | * @dev: the display device | |
115 | * @attr: the display message attribute | |
116 | * @buf: the buffer to read the message into | |
117 | * | |
118 | * Read the current message being displayed or scrolled across the display into | |
119 | * @buf, for reads from sysfs. | |
120 | * | |
121 | * Return: the number of characters written to @buf | |
122 | */ | |
123 | static ssize_t message_show(struct device *dev, struct device_attribute *attr, | |
124 | char *buf) | |
125 | { | |
126 | struct linedisp *linedisp = container_of(dev, struct linedisp, dev); | |
127 | ||
128 | return sysfs_emit(buf, "%s\n", linedisp->message); | |
129 | } | |
130 | ||
131 | /** | |
132 | * message_store() - write a new message via sysfs | |
133 | * @dev: the display device | |
134 | * @attr: the display message attribute | |
135 | * @buf: the buffer containing the new message | |
136 | * @count: the size of the message in @buf | |
137 | * | |
138 | * Write a new message to display or scroll across the display from sysfs. | |
139 | * | |
140 | * Return: the size of the message on success, else -ERRNO | |
141 | */ | |
142 | static ssize_t message_store(struct device *dev, struct device_attribute *attr, | |
143 | const char *buf, size_t count) | |
144 | { | |
145 | struct linedisp *linedisp = container_of(dev, struct linedisp, dev); | |
146 | int err; | |
147 | ||
148 | err = linedisp_display(linedisp, buf, count); | |
149 | return err ?: count; | |
150 | } | |
151 | ||
152 | static DEVICE_ATTR_RW(message); | |
153 | ||
d79141c3 GU |
154 | static ssize_t scroll_step_ms_show(struct device *dev, |
155 | struct device_attribute *attr, char *buf) | |
156 | { | |
157 | struct linedisp *linedisp = container_of(dev, struct linedisp, dev); | |
158 | ||
159 | return sysfs_emit(buf, "%u\n", jiffies_to_msecs(linedisp->scroll_rate)); | |
160 | } | |
161 | ||
162 | static ssize_t scroll_step_ms_store(struct device *dev, | |
163 | struct device_attribute *attr, | |
164 | const char *buf, size_t count) | |
165 | { | |
166 | struct linedisp *linedisp = container_of(dev, struct linedisp, dev); | |
167 | unsigned int ms; | |
168 | ||
169 | if (kstrtouint(buf, 10, &ms) != 0) | |
170 | return -EINVAL; | |
171 | ||
172 | linedisp->scroll_rate = msecs_to_jiffies(ms); | |
173 | if (linedisp->message && linedisp->message_len > linedisp->num_chars) { | |
174 | del_timer_sync(&linedisp->timer); | |
175 | if (linedisp->scroll_rate) | |
176 | linedisp_scroll(&linedisp->timer); | |
177 | } | |
178 | ||
179 | return count; | |
180 | } | |
181 | ||
182 | static DEVICE_ATTR_RW(scroll_step_ms); | |
183 | ||
7e76aece GU |
184 | static struct attribute *linedisp_attrs[] = { |
185 | &dev_attr_message.attr, | |
d79141c3 | 186 | &dev_attr_scroll_step_ms.attr, |
7e76aece GU |
187 | NULL, |
188 | }; | |
189 | ATTRIBUTE_GROUPS(linedisp); | |
190 | ||
191 | static const struct device_type linedisp_type = { | |
192 | .groups = linedisp_groups, | |
193 | }; | |
194 | ||
195 | /** | |
196 | * linedisp_register - register a character line display | |
197 | * @linedisp: pointer to character line display structure | |
198 | * @parent: parent device | |
199 | * @num_chars: the number of characters that can be displayed | |
200 | * @buf: pointer to a buffer that can hold @num_chars characters | |
201 | * @update: Function called to update the display. This must not sleep! | |
202 | * | |
203 | * Return: zero on success, else a negative error code. | |
204 | */ | |
205 | int linedisp_register(struct linedisp *linedisp, struct device *parent, | |
206 | unsigned int num_chars, char *buf, | |
207 | void (*update)(struct linedisp *linedisp)) | |
208 | { | |
209 | static atomic_t linedisp_id = ATOMIC_INIT(-1); | |
210 | int err; | |
211 | ||
212 | memset(linedisp, 0, sizeof(*linedisp)); | |
213 | linedisp->dev.parent = parent; | |
214 | linedisp->dev.type = &linedisp_type; | |
215 | linedisp->update = update; | |
216 | linedisp->buf = buf; | |
217 | linedisp->num_chars = num_chars; | |
d79141c3 | 218 | linedisp->scroll_rate = DEFAULT_SCROLL_RATE; |
7e76aece GU |
219 | |
220 | device_initialize(&linedisp->dev); | |
221 | dev_set_name(&linedisp->dev, "linedisp.%lu", | |
222 | (unsigned long)atomic_inc_return(&linedisp_id)); | |
223 | ||
224 | /* initialise a timer for scrolling the message */ | |
225 | timer_setup(&linedisp->timer, linedisp_scroll, 0); | |
226 | ||
227 | err = device_add(&linedisp->dev); | |
228 | if (err) | |
229 | goto out_del_timer; | |
230 | ||
231 | /* display a default message */ | |
232 | err = linedisp_display(linedisp, "Linux " UTS_RELEASE " ", -1); | |
233 | if (err) | |
234 | goto out_del_dev; | |
235 | ||
236 | return 0; | |
237 | ||
238 | out_del_dev: | |
239 | device_del(&linedisp->dev); | |
240 | out_del_timer: | |
241 | del_timer_sync(&linedisp->timer); | |
242 | put_device(&linedisp->dev); | |
243 | return err; | |
244 | } | |
245 | EXPORT_SYMBOL_GPL(linedisp_register); | |
246 | ||
247 | /** | |
248 | * linedisp_unregister - unregister a character line display | |
249 | * @linedisp: pointer to character line display structure registered previously | |
250 | * with linedisp_register() | |
251 | */ | |
252 | void linedisp_unregister(struct linedisp *linedisp) | |
253 | { | |
254 | device_del(&linedisp->dev); | |
255 | del_timer_sync(&linedisp->timer); | |
256 | kfree(linedisp->message); | |
257 | put_device(&linedisp->dev); | |
258 | } | |
259 | EXPORT_SYMBOL_GPL(linedisp_unregister); | |
260 | ||
261 | MODULE_LICENSE("GPL"); |