1 /*
2 * drivers/gpio/max7301.c
3 *
4 * Copyright (C) 2006 Juergen Beisert, Pengutronix
5 * Copyright (C) 2008 Guennadi Liakhovetski, Pengutronix
6 * Copyright (C) 2009 Wolfram Sang, Pengutronix
7 *
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License version 2 as
10 * published by the Free Software Foundation.
11 *
12 * Check max730x.c for further details.
13 */
14
15 #include <linux/module.h>
16 #include <linux/init.h>
17 #include <linux/platform_device.h>
18 #include <linux/mutex.h>
19 #include <linux/slab.h>
20 #include <linux/spi/spi.h>
21 #include <linux/spi/max7301.h>
22
23 /* A write to the MAX7301 means one message with one transfer */
max7301_spi_write(struct device * dev,unsigned int reg,unsigned int val)24 static int max7301_spi_write(struct device *dev, unsigned int reg,
25 unsigned int val)
26 {
27 struct spi_device *spi = to_spi_device(dev);
28 u16 word = ((reg & 0x7F) << 8) | (val & 0xFF);
29
30 return spi_write(spi, (const u8 *)&word, sizeof(word));
31 }
32
33 /* A read from the MAX7301 means two transfers; here, one message each */
34
max7301_spi_read(struct device * dev,unsigned int reg)35 static int max7301_spi_read(struct device *dev, unsigned int reg)
36 {
37 int ret;
38 u16 word;
39 struct spi_device *spi = to_spi_device(dev);
40
41 word = 0x8000 | (reg << 8);
42 ret = spi_write(spi, (const u8 *)&word, sizeof(word));
43 if (ret)
44 return ret;
45 /*
46 * This relies on the fact, that a transfer with NULL tx_buf shifts out
47 * zero bytes (=NOOP for MAX7301)
48 */
49 ret = spi_read(spi, (u8 *)&word, sizeof(word));
50 if (ret)
51 return ret;
52 return word & 0xff;
53 }
54
max7301_probe(struct spi_device * spi)55 static int __devinit max7301_probe(struct spi_device *spi)
56 {
57 struct max7301 *ts;
58 int ret;
59
60 /* bits_per_word cannot be configured in platform data */
61 spi->bits_per_word = 16;
62 ret = spi_setup(spi);
63 if (ret < 0)
64 return ret;
65
66 ts = kzalloc(sizeof(struct max7301), GFP_KERNEL);
67 if (!ts)
68 return -ENOMEM;
69
70 ts->read = max7301_spi_read;
71 ts->write = max7301_spi_write;
72 ts->dev = &spi->dev;
73
74 ret = __max730x_probe(ts);
75 if (ret)
76 kfree(ts);
77 return ret;
78 }
79
max7301_remove(struct spi_device * spi)80 static int __devexit max7301_remove(struct spi_device *spi)
81 {
82 return __max730x_remove(&spi->dev);
83 }
84
85 static const struct spi_device_id max7301_id[] = {
86 { "max7301", 0 },
87 { }
88 };
89 MODULE_DEVICE_TABLE(spi, max7301_id);
90
91 static struct spi_driver max7301_driver = {
92 .driver = {
93 .name = "max7301",
94 .owner = THIS_MODULE,
95 },
96 .probe = max7301_probe,
97 .remove = __devexit_p(max7301_remove),
98 .id_table = max7301_id,
99 };
100
max7301_init(void)101 static int __init max7301_init(void)
102 {
103 return spi_register_driver(&max7301_driver);
104 }
105 /* register after spi postcore initcall and before
106 * subsys initcalls that may rely on these GPIOs
107 */
108 subsys_initcall(max7301_init);
109
max7301_exit(void)110 static void __exit max7301_exit(void)
111 {
112 spi_unregister_driver(&max7301_driver);
113 }
114 module_exit(max7301_exit);
115
116 MODULE_AUTHOR("Juergen Beisert, Wolfram Sang");
117 MODULE_LICENSE("GPL v2");
118 MODULE_DESCRIPTION("MAX7301 GPIO-Expander");
119