1 // SPDX-License-Identifier: GPL-2.0-or-later
3  * Character line display core support
20 #include "line-display.h"
25  * linedisp_scroll() - scroll the display by a character
26  * @t: really a pointer to the private data structure
28  * Scroll the current message along the display by one character, rearming the
34 	unsigned int i, ch = linedisp->scroll_pos;  in linedisp_scroll()
35 	unsigned int num_chars = linedisp->num_chars;  in linedisp_scroll()
40 		for (; i < num_chars && ch < linedisp->message_len; i++, ch++)  in linedisp_scroll()
41 			linedisp->buf[i] = linedisp->message[ch];  in linedisp_scroll()
47 	/* update the display */  in linedisp_scroll()
48 	linedisp->update(linedisp);  in linedisp_scroll()
51 	linedisp->scroll_pos++;  in linedisp_scroll()
52 	linedisp->scroll_pos %= linedisp->message_len;  in linedisp_scroll()
55 	if (linedisp->message_len > num_chars && linedisp->scroll_rate)  in linedisp_scroll()
56 		mod_timer(&linedisp->timer, jiffies + linedisp->scroll_rate);  in linedisp_scroll()
60  * linedisp_display() - set the message to be displayed
62  * @msg: the message to display
63  * @count: length of msg, or -1
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.
69  * Return: 0 on success, -ENOMEM on memory allocation failure
77 	del_timer_sync(&linedisp->timer);  in linedisp_display()
79 	if (count == -1)  in linedisp_display()
82 	/* if the string ends with a newline, trim it */  in linedisp_display()
83 	if (msg[count - 1] == '\n')  in linedisp_display()
84 		count--;  in linedisp_display()
87 		/* Clear the display */  in linedisp_display()
88 		kfree(linedisp->message);  in linedisp_display()
89 		linedisp->message = NULL;  in linedisp_display()
90 		linedisp->message_len = 0;  in linedisp_display()
91 		memset(linedisp->buf, ' ', linedisp->num_chars);  in linedisp_display()
92 		linedisp->update(linedisp);  in linedisp_display()
98 		return -ENOMEM;  in linedisp_display()
100 	kfree(linedisp->message);  in linedisp_display()
102 	linedisp->message = new_msg;  in linedisp_display()
103 	linedisp->message_len = count;  in linedisp_display()
104 	linedisp->scroll_pos = 0;  in linedisp_display()
106 	/* update the display */  in linedisp_display()
107 	linedisp_scroll(&linedisp->timer);  in linedisp_display()
113  * message_show() - read message via sysfs
114  * @dev: the display device
115  * @attr: the display message attribute
118  * Read the current message being displayed or scrolled across the display into
128 	return sysfs_emit(buf, "%s\n", linedisp->message);  in message_show()
132  * message_store() - write a new message via sysfs
133  * @dev: the display device
134  * @attr: the display message attribute
138  * Write a new message to display or scroll across the display from sysfs.
140  * Return: the size of the message on success, else -ERRNO
159 	return sysfs_emit(buf, "%u\n", jiffies_to_msecs(linedisp->scroll_rate));  in scroll_step_ms_show()
170 		return -EINVAL;  in scroll_step_ms_store()
172 	linedisp->scroll_rate = msecs_to_jiffies(ms);  in scroll_step_ms_store()
173 	if (linedisp->message && linedisp->message_len > linedisp->num_chars) {  in scroll_step_ms_store()
174 		del_timer_sync(&linedisp->timer);  in scroll_step_ms_store()
175 		if (linedisp->scroll_rate)  in scroll_step_ms_store()
176 			linedisp_scroll(&linedisp->timer);  in scroll_step_ms_store()
196  * linedisp_register - register a character line display
197  * @linedisp: pointer to character line display structure
200  * @buf: pointer to a buffer that can hold @num_chars characters
201  * @update: Function called to update the display.  This must not sleep!
203  * Return: zero on success, else a negative error code.
209 	static atomic_t linedisp_id = ATOMIC_INIT(-1);  in linedisp_register()
213 	linedisp->dev.parent = parent;  in linedisp_register()
214 	linedisp->dev.type = &linedisp_type;  in linedisp_register()
215 	linedisp->update = update;  in linedisp_register()
216 	linedisp->buf = buf;  in linedisp_register()
217 	linedisp->num_chars = num_chars;  in linedisp_register()
218 	linedisp->scroll_rate = DEFAULT_SCROLL_RATE;  in linedisp_register()
220 	device_initialize(&linedisp->dev);  in linedisp_register()
221 	dev_set_name(&linedisp->dev, "linedisp.%lu",  in linedisp_register()
224 	/* initialise a timer for scrolling the message */  in linedisp_register()
225 	timer_setup(&linedisp->timer, linedisp_scroll, 0);  in linedisp_register()
227 	err = device_add(&linedisp->dev);  in linedisp_register()
231 	/* display a default message */  in linedisp_register()
232 	err = linedisp_display(linedisp, "Linux " UTS_RELEASE "       ", -1);  in linedisp_register()
239 	device_del(&linedisp->dev);  in linedisp_register()
241 	del_timer_sync(&linedisp->timer);  in linedisp_register()
242 	put_device(&linedisp->dev);  in linedisp_register()
248  * linedisp_unregister - unregister a character line display
249  * @linedisp: pointer to character line display structure registered previously
254 	device_del(&linedisp->dev);  in linedisp_unregister()
255 	del_timer_sync(&linedisp->timer);  in linedisp_unregister()
256 	kfree(linedisp->message);  in linedisp_unregister()
257 	put_device(&linedisp->dev);  in linedisp_unregister()