1 | #ifndef RTEMS_LIBI2C_H |
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2 | #define RTEMS_LIBI2C_H |
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3 | /*$Id$*/ |
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4 | #include <rtems.h> |
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5 | |
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6 | #include <rtems/io.h> |
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7 | |
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8 | #ifdef __cplusplus |
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9 | extern "C" { |
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10 | #endif |
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11 | |
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12 | /* Simple I2C driver API */ |
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13 | |
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14 | /* Initialize the libary - may fail if no semaphore or no driver slot is available */ |
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15 | int rtems_libi2c_initialize (); |
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16 | |
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17 | /* Bus Driver API |
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18 | * |
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19 | * Bus drivers provide access to low-level i2c functions |
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20 | * such as 'send start', 'send address', 'get bytes' etc. |
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21 | */ |
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22 | |
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23 | /* first field must be a pointer to ops; driver |
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24 | * may add its own fields after this. |
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25 | * the struct that is registered with the library |
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26 | * is not copied; a pointer will we passed |
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27 | * to the callback functions (ops). |
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28 | */ |
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29 | typedef struct rtems_libi2c_bus_t_ |
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30 | { |
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31 | struct rtems_libi2c_bus_ops_ *ops; |
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32 | int size; /* size of whole structure */ |
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33 | } rtems_libi2c_bus_t; |
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34 | |
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35 | /* Access functions a low level driver must provide; |
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36 | * |
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37 | * All of these, except read_bytes and write_bytes |
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38 | * return RTEMS_SUCCESSFUL on success and an error status |
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39 | * otherwise. The read and write ops return the number |
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40 | * of chars read/written or -(status code) on error. |
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41 | */ |
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42 | typedef struct rtems_libi2c_bus_ops_ |
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43 | { |
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44 | /* Initialize the bus; might be called again to reset the bus driver */ |
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45 | rtems_status_code (*init) (rtems_libi2c_bus_t * bushdl); |
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46 | /* Send start condition */ |
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47 | rtems_status_code (*send_start) (rtems_libi2c_bus_t * bushdl); |
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48 | /* Send stop condition */ |
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49 | rtems_status_code (*send_stop) (rtems_libi2c_bus_t * bushdl); |
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50 | /* initiate transfer from (rw!=0) or to a device */ |
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51 | rtems_status_code (*send_addr) (rtems_libi2c_bus_t * bushdl, |
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52 | uint32_t addr, int rw); |
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53 | /* read a number of bytes */ |
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54 | int (*read_bytes) (rtems_libi2c_bus_t * bushdl, unsigned char *bytes, |
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55 | int nbytes); |
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56 | /* write a number of bytes */ |
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57 | int (*write_bytes) (rtems_libi2c_bus_t * bushdl, unsigned char *bytes, |
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58 | int nbytes); |
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59 | } rtems_libi2c_bus_ops_t; |
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60 | |
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61 | |
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62 | /* |
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63 | * Register a lowlevel driver |
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64 | * |
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65 | * TODO: better description |
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66 | * |
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67 | * This allocates a major number identifying *this* driver |
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68 | * (i.e., libi2c) and the minor number encodes a bus# and a i2c address. |
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69 | * |
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70 | * The name will be registered in the filesystem (parent |
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71 | * directories must exist). It may be NULL in which case |
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72 | * the library will pick a default. |
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73 | * |
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74 | * RETURNS: bus # (>=0) or -1 on error (errno set). |
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75 | */ |
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76 | |
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77 | int rtems_libi2c_register_bus (char *name, rtems_libi2c_bus_t * bus); |
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78 | |
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79 | extern rtems_device_major_number rtems_libi2c_major; |
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80 | |
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81 | #define RTEMS_LIBI2C_MAKE_MINOR(busno, i2caddr) \ |
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82 | ((((busno)&((1<<3)-1))<<10) | ((i2caddr)&((1<<10)-1))) |
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83 | |
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84 | /* After the library is initialized, a major number is available. |
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85 | * As soon as a low-level bus driver is registered (above routine |
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86 | * returns a 'busno'), a device node can be created in the filesystem |
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87 | * with a major/minor number pair of |
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88 | * |
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89 | * rtems_libi2c_major / RTEMS_LIBI2C_MAKE_MINOR(busno, i2caddr) |
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90 | * |
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91 | * and a 'raw' hi-level driver is then attached to this device |
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92 | * node. |
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93 | * This 'raw' driver has very simple semantics: |
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94 | * |
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95 | * 'open' sends a start condition |
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96 | * 'read'/'write' address the device identified by the i2c bus# and address |
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97 | * encoded in the minor number and read or write, respectively |
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98 | * a stream of bytes from or to the device. Every time the |
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99 | * direction is changed, a 're-start' condition followed by |
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100 | * an 'address' cycle is generated on the i2c bus. |
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101 | * 'close' sends a stop condition. |
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102 | * |
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103 | * Hence, using the 'raw' driver, e.g., 100 bytes at offset 0x200 can be |
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104 | * read from an EEPROM by the following pseudo-code: |
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105 | * |
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106 | * mknod("/dev/i2c-54", mode, MKDEV(rtems_libi2c_major, RTEMS_LIBI2C_MAKE_MINOR(0,0x54))) |
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107 | * |
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108 | * int fd; |
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109 | * char off[2]={0x02,0x00}; |
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110 | * |
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111 | * fd = open("/dev/i2c-54",O_RDWR); |
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112 | * write(fd,off,2); |
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113 | * read(fd,buf,100); |
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114 | * close(fd); |
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115 | * |
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116 | */ |
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117 | |
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118 | /* Higher Level Driver API |
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119 | * |
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120 | * Higher level drivers know how to deal with specific i2c |
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121 | * devices (independent of the bus interface chip) and provide |
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122 | * an abstraction, i.e., the usual read/write/ioctl access. |
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123 | * |
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124 | * Using the above example, such a high level driver could |
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125 | * prevent the user from issuing potentially destructive write |
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126 | * operations (the aforementioned EEPROM interprets any 3rd |
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127 | * and following byte written to the device as data, i.e., the |
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128 | * contents could easily be changed!). |
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129 | * The correct 'read-pointer offset' programming could be |
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130 | * implemented in 'open' and 'ioctl' of a high-level driver and |
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131 | * the user would then only have to perform harmless read |
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132 | * operations, e.g., |
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133 | * |
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134 | * fd = open("/dev/i2c.eeprom",O_RDONLY) / * opens and sets EEPROM read pointer * / |
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135 | * ioctl(fd, IOCTL_SEEK, 0x200) / * repositions the read pointer * / |
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136 | * read(fd, buf, 100) |
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137 | * close(fd) |
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138 | * |
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139 | */ |
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140 | |
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141 | /* struct provided at driver registration. The driver may store |
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142 | * private data behind the mandatory first fields but the size |
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143 | * must be set to the size of the entire struct, e.g., |
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144 | * |
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145 | * struct driver_pvt { |
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146 | * rtems_libi2c_drv_t pub; |
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147 | * struct { ... } pvt; |
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148 | * } my_driver = { |
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149 | * { ops: my_ops, |
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150 | * size: sizeof(my_driver) |
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151 | * }, |
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152 | * { ...}; |
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153 | * }; |
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154 | * |
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155 | * A pointer to this struct is passed to the callback ops. |
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156 | */ |
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157 | |
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158 | typedef struct rtems_libi2c_drv_t_ |
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159 | { |
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160 | rtems_driver_address_table *ops; /* the driver ops */ |
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161 | int size; /* size of whole structure (including appended private data) */ |
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162 | } rtems_libi2c_drv_t; |
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163 | |
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164 | /* |
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165 | * The high level driver must be registered with a particular |
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166 | * bus number and i2c address. |
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167 | * |
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168 | * The registration procedure also creates a filesystem node, |
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169 | * i.e., the returned minor number is not really needed. |
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170 | * |
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171 | * If the 'name' argument is NULL, no filesystem node is |
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172 | * created (but this can be done 'manually' using rtems_libi2c_major |
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173 | * and the return value of this routine). |
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174 | * |
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175 | * RETURNS minor number (FYI) or -1 on failure |
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176 | */ |
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177 | int |
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178 | rtems_libi2c_register_drv (char *name, rtems_libi2c_drv_t * drvtbl, |
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179 | unsigned bus, unsigned i2caddr); |
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180 | |
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181 | /* Operations available to high level drivers */ |
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182 | |
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183 | /* NOTES: The bus a device is attached to is LOCKED from the first send_start |
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184 | * until send_stop is executed! |
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185 | * |
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186 | * Bus tenure MUST NOT span multiple system calls - otherwise, a single |
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187 | * thread could get into the protected sections (or would deadlock if the |
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188 | * mutex was not nestable). |
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189 | * E.g., consider what happens if 'open' sends a 'start' and 'close' |
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190 | * sends a 'stop' (i.e., the bus mutex would be locked in 'open' and |
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191 | * released in 'close'. A single thread could try to open two devices |
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192 | * on the same bus and would either deadlock or nest into the bus mutex |
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193 | * and potentially mess up the i2c messages. |
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194 | * |
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195 | * The correct way is to *always* relinquish the i2c bus (i.e., send 'stop' |
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196 | * from any driver routine prior to returning control to the caller. |
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197 | * Consult the implementation of the generic driver routines (open, close, ...) |
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198 | * below or the examples in i2c-2b-eeprom.c and i2c-2b-ds1621.c |
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199 | * |
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200 | * Drivers just pass the minor number on to these routines... |
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201 | */ |
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202 | rtems_status_code rtems_libi2c_send_start (rtems_device_minor_number minor); |
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203 | |
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204 | rtems_status_code rtems_libi2c_send_stop (rtems_device_minor_number minor); |
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205 | |
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206 | rtems_status_code |
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207 | rtems_libi2c_send_addr (rtems_device_minor_number minor, int rw); |
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208 | |
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209 | /* the read/write routines return the number of bytes transferred |
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210 | * or -(status_code) on error. |
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211 | */ |
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212 | int |
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213 | rtems_libi2c_read_bytes (rtems_device_minor_number minor, |
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214 | unsigned char *bytes, int nbytes); |
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215 | |
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216 | int |
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217 | rtems_libi2c_write_bytes (rtems_device_minor_number minor, |
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218 | unsigned char *bytes, int nbytes); |
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219 | |
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220 | /* Send start, send address and read bytes */ |
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221 | int |
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222 | rtems_libi2c_start_read_bytes (uint32_t minor, unsigned char *bytes, |
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223 | int nbytes); |
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224 | |
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225 | /* Send start, send address and write bytes */ |
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226 | int |
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227 | rtems_libi2c_start_write_bytes (uint32_t minor, unsigned char *bytes, |
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228 | int nbytes); |
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229 | |
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230 | #ifdef __cplusplus |
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231 | } |
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232 | #endif |
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233 | |
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234 | #endif |
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