xref: /linux/drivers/i2c/i2c-boardinfo.c (revision d39d0ed196aa1685bb24771e92f78633c66ac9cb)
1 /*
2  * i2c-boardinfo.h - collect pre-declarations of I2C devices
3  *
4  * This program is free software; you can redistribute it and/or modify
5  * it under the terms of the GNU General Public License as published by
6  * the Free Software Foundation; either version 2 of the License, or
7  * (at your option) any later version.
8  *
9  * This program is distributed in the hope that it will be useful,
10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12  * GNU General Public License for more details.
13  *
14  * You should have received a copy of the GNU General Public License
15  * along with this program; if not, write to the Free Software
16  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
17  */
18 
19 #include <linux/kernel.h>
20 #include <linux/i2c.h>
21 #include <linux/slab.h>
22 #include <linux/rwsem.h>
23 
24 #include "i2c-core.h"
25 
26 
27 /* These symbols are exported ONLY FOR the i2c core.
28  * No other users will be supported.
29  */
30 DECLARE_RWSEM(__i2c_board_lock);
31 EXPORT_SYMBOL_GPL(__i2c_board_lock);
32 
33 LIST_HEAD(__i2c_board_list);
34 EXPORT_SYMBOL_GPL(__i2c_board_list);
35 
36 int __i2c_first_dynamic_bus_num;
37 EXPORT_SYMBOL_GPL(__i2c_first_dynamic_bus_num);
38 
39 
40 /**
41  * i2c_register_board_info - statically declare I2C devices
42  * @busnum: identifies the bus to which these devices belong
43  * @info: vector of i2c device descriptors
44  * @len: how many descriptors in the vector; may be zero to reserve
45  *	the specified bus number.
46  *
47  * Systems using the Linux I2C driver stack can declare tables of board info
48  * while they initialize.  This should be done in board-specific init code
49  * near arch_initcall() time, or equivalent, before any I2C adapter driver is
50  * registered.  For example, mainboard init code could define several devices,
51  * as could the init code for each daughtercard in a board stack.
52  *
53  * The I2C devices will be created later, after the adapter for the relevant
54  * bus has been registered.  After that moment, standard driver model tools
55  * are used to bind "new style" I2C drivers to the devices.  The bus number
56  * for any device declared using this routine is not available for dynamic
57  * allocation.
58  *
59  * The board info passed can safely be __initdata, but be careful of embedded
60  * pointers (for platform_data, functions, etc) since that won't be copied.
61  */
62 int __init
63 i2c_register_board_info(int busnum,
64 	struct i2c_board_info const *info, unsigned len)
65 {
66 	int status;
67 
68 	down_write(&__i2c_board_lock);
69 
70 	/* dynamic bus numbers will be assigned after the last static one */
71 	if (busnum >= __i2c_first_dynamic_bus_num)
72 		__i2c_first_dynamic_bus_num = busnum + 1;
73 
74 	for (status = 0; len; len--, info++) {
75 		struct i2c_devinfo	*devinfo;
76 
77 		devinfo = kzalloc(sizeof(*devinfo), GFP_KERNEL);
78 		if (!devinfo) {
79 			pr_debug("i2c-core: can't register boardinfo!\n");
80 			status = -ENOMEM;
81 			break;
82 		}
83 
84 		devinfo->busnum = busnum;
85 		devinfo->board_info = *info;
86 		list_add_tail(&devinfo->list, &__i2c_board_list);
87 	}
88 
89 	up_write(&__i2c_board_lock);
90 
91 	return status;
92 }
93