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