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