/share/man/man4/iic.4

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  1. .\" Copyright (c) 2006, M. Warner Losh
  2. .\" Copyright (c) 1998, Nicolas Souchu
  3. .\" All rights reserved.
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  28. .Dd September 6, 2006
  29. .Dt IIC 4
  30. .Os
  31. .Sh NAME
  32. .Nm iic
  33. .Nd I2C generic I/O device driver
  34. .Sh SYNOPSIS
  35. .Cd "device iic"
  36. .Pp
  37. .In dev/iicbus/iic.h
  38. .Sh DESCRIPTION
  39. The
  40. .Nm
  41. device driver provides generic I/O to any
  42. .Xr iicbus 4
  43. instance.
  44. In order to control I2C devices, use
  45. .Pa /dev/iic?
  46. with the
  47. following ioctls:
  48. .Bl -tag -width ".Dv I2CRPTSTART"
  49. .It Dv I2CSTART
  50. .Pq Vt "struct iiccmd"
  51. Sends the start condition to the slave specified by the
  52. .Va slave
  53. element to the bus.
  54. All other elements are ignored.
  55. .It Dv I2CRPTSTART
  56. .Pq Vt "struct iiccmd"
  57. Sends the repeated start condition to the slave specified by the
  58. .Va slave
  59. element to the bus.
  60. All other elements are ignored.
  61. .It Dv I2CSTOP
  62. No argument is passed.
  63. Sends the stop condition to the bus.
  64. This terminates the current transaction.
  65. .It Dv I2CRSTCARD
  66. .Pq Vt "struct iiccmd"
  67. Resets the bus.
  68. The argument is completely ignored.
  69. .It Dv I2CWRITE
  70. .Pq Vt "struct iiccmd"
  71. Writes data to the
  72. .Xr iicbus 4 .
  73. The bus should already be started.
  74. The
  75. .Va slave
  76. element is ignored.
  77. The
  78. .Va count
  79. element is the number of bytes to write.
  80. The
  81. .Va last
  82. element is a boolean flag.
  83. It is non-zero when additional write commands will follow.
  84. The
  85. .Va buf
  86. element is a pointer to the data to write to the bus.
  87. .It Dv I2CREAD
  88. .Pq Vt "struct iiccmd"
  89. Reads data from the
  90. .Xr iicbus 4 .
  91. The bus should already be started.
  92. The
  93. .Va slave
  94. element is ignored.
  95. The
  96. .Va count
  97. element is the number of bytes to write.
  98. The
  99. .Va last
  100. element is a boolean flag.
  101. It is non-zero when additional write commands will follow.
  102. The
  103. .Va buf
  104. element is a pointer to where to store the data read from the bus.
  105. Short reads on the bus produce undefined results.
  106. .It Dv I2CRDWR
  107. .Pq Vt "struct iic_rdwr_data"
  108. Generic read/write interface.
  109. Allows for an arbitrary number of commands to be sent to
  110. an arbitrary number of devices on the bus.
  111. A read transfer is specified if
  112. .Dv IIC_M_RD
  113. is set in
  114. .Va flags .
  115. Otherwise the transfer is a write transfer.
  116. The
  117. .Va slave
  118. element specifies the 7-bit address for the transfer.
  119. The
  120. .Va len
  121. element is the length of the data.
  122. The
  123. .Va buf
  124. element is a buffer for that data.
  125. This ioctl is intended to be
  126. .Tn Linux
  127. compatible.
  128. .El
  129. .Pp
  130. The following data structures are defined in
  131. .In dev/iicbus/iic.h
  132. and referenced above:
  133. .Bd -literal -offset indent
  134. struct iiccmd {
  135. u_char slave;
  136. int count;
  137. int last;
  138. char *buf;
  139. };
  140. /* Designed to be compatible with linux's struct i2c_msg */
  141. struct iic_msg
  142. {
  143. uint16_t slave;
  144. uint16_t flags;
  145. #define IIC_M_RD 0x0001 /* read vs write */
  146. uint16_t len; /* msg length */
  147. uint8_t * buf;
  148. };
  149. struct iic_rdwr_data {
  150. struct iic_msg *msgs;
  151. uint32_t nmsgs;
  152. };
  153. .Ed
  154. .Pp
  155. It is also possible to use read/write routines, then I2C start/stop handshake is
  156. managed by the
  157. .Xr iicbus 4
  158. system.
  159. However, the address used for the read/write routines is the one
  160. passed to last
  161. .Dv I2CSTART
  162. .Xr ioctl 2
  163. to this device.
  164. .Sh SEE ALSO
  165. .Xr ioctl 2 ,
  166. .Xr read 2 ,
  167. .Xr write 2 ,
  168. .Xr iicbus 4
  169. .Sh HISTORY
  170. The
  171. .Nm
  172. manual page first appeared in
  173. .Fx 3.0 .
  174. .Sh AUTHORS
  175. .An -nosplit
  176. This
  177. manual page was written by
  178. .An Nicolas Souchu
  179. and
  180. .An M. Warner Losh .
  181. .Sh BUGS
  182. Only the
  183. .Dv I2CRDWR
  184. .Xr ioctl 2
  185. is thread safe.
  186. All other interfaces suffer from some kind of race.