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  18 .Dd August 31, 2018
  19 .Dt PRNIO 7I
  20 .Os
  21 .Sh NAME
  22 .Nm prnio
  23 .Nd generic printer interface
  24 .Sh SYNOPSIS
  25 .In sys/prnio.h
  26 .Sh DESCRIPTION
  27 The
  28 .Nm
  29 generic printer interface defines ioctl commands and data
  30 structures for printer device drivers.
  31 .Pp
  32 .Nm
  33 defines and provides facilities for five basic phases of the printing process:
  34 .Bl -bullet -offset indent
  35 .It
  36 Identification \(em Retrieve device information/attributes
  37 .It
  38 Setup \(em Set device attributes
  39 .It
  40 Transfer \(em Transfer data to or from the device
  41 .It
  42 Cleanup \(em Transfer phase conclusion
  43 .It
  44 Abort \(em Transfer phase interruption
  45 .El
  46 .Pp
  47 During the Identification phase, the application retrieves a set of device
  48 capabilities and additional information using the
  49 .Dv PRNIOC_GET_IFCAP ,
  50 .Dv PRNIOC_GET_STATUS ,
  51 .Dv PRNIOC_GET_TIMEOUTS ,
  52 .Dv PRNIOC_GET_IFINFO ,
  53 and
  54 .Dv PRNIOC_GET_1284_DEVID
  55 commands.
  56 .Pp
  57 During the Setup phase the application sets some interface attributes and
  58 probably resets the printer as described in the
  59 .Dv PRNIOC_SET_IFCAP ,
  60 .Dv PRNIOC_SET_TIMEOUTS ,
  61 and
  62 .Dv PRNIOC_RESET
  63 sections.
  64 .Pp
  65 During the Transfer phase, data is transferred in a forward (host to
  66 peripheral) or reverse direction (peripheral to host).
  67 Transfer is accomplished
  68 using
  69 .Xr write 2
  70 and
  71 .Xr read 2
  72 system calls.
  73 For
  74 .Nm
  75 compliant
  76 printer drivers, forward transfer support is mandatory, while reverse transfer
  77 support is optional.
  78 Applications can also use
  79 .Dv PRNIOC_GET_STATUS
  80 and
  81 .Dv PRNIOC_GET_1284_STATUS
  82 commands during the transfer to monitor the device state.
  83 .Pp
  84 The Cleanup phase is accomplished by closing the device using
  85 .Xr close 2 .
  86 Device drivers supporting
  87 .Nm
  88 may set non-zero error code as appropriate.
  89 Applications should explicitly
  90 .Xr close 2
  91 a device before
  92 exiting and check
  93 .Va errno
  94 value.
  95 .Pp
  96 The Abort phase is accomplished by interrupting the
  97 .Xr write 2
  98 and
  99 .Xr read 2
 100 system calls.
 101 The application can perform some additional cleanup
 102 during the Abort phase as described in
 103 .Dv PRNIOC_GET_IFCAP
 104 section.
 105 .Sh IOCTLS
 106 .Bl -tag -width PRNIOC_GET_IFINFO
 107 .It Dv PRNIOC_GET_IFCAP
 108 Application can retrieve printer interface capabilities using this command.
 109 The
 110 .Xr ioctl 2
 111 argument is a pointer to
 112 .Vt uint_t ,
 113 a bit field representing
 114 a set of properties and services provided by a printer driver.
 115 Set bit means supported capability.
 116 The following values are defined:
 117 .Bl -tag -width PRN_1284_STATUS
 118 .It Dv PRN_BIDI
 119 When this bit is set, the interface operates in a
 120 bidirectional mode, instead of forward-only mode.
 121 .It Dv PRN_HOTPLUG
 122 If this bit is set, the interface allows device hot-plugging.
 123 .It Dv PRN_1284_DEVID
 124 If this bit is set, the device is capable of returning
 125 .Em 1284
 126 device ID (see
 127 .Dv PRNIOC_GET_1284_DEVID ) .
 128 .It Dv PRN_1284_STATUS
 129 If this bit is set, the device driver can return device
 130 status lines (see
 131 .Dv PRNIOC_GET_1284_STATUS ) .
 132 Some devices support this
 133 ioctl in unidirectional mode only.
 134 .It Dv PRN_TIMEOUTS
 135 If this bit is set the peripheral may stall during the
 136 transfer phase and the driver can timeout and return from the
 137 .Xr write 2
 138 and
 139 .Xr read 2
 140 returning the number of bytes that have been transferred.
 141 If
 142 .Dv PRN_TIMEOUTS
 143 is set, the driver supports this functionality and the
 144 timeout values can be retrieved and modified via the
 145 .Dv PRNIOC_GET_TIMEOUTS
 146 and
 147 .Dv PRNIOC_SET_TIMEOUTS
 148 ioctls.
 149 Otherwise, applications can implement
 150 their own timeouts and abort phase.
 151 .It Dv PRN_STREAMS
 152 This bit impacts the application abort phase behaviour.
 153 If the device claimed
 154 .Dv PRN_STREAMS
 155 capability, the application must issue an
 156 .Dv I_FLUSH
 157 .Xr ioctl 2
 158 before
 159 .Xr close 2
 160 to dismiss the untransferred
 161 data.
 162 Only STREAMS drivers can support this capability.
 163 .El
 164 .It Dv PRNIOC_SET_IFCAP
 165 This ioctl can be used to change interface capabilities.
 166 The argument is a pointer to
 167 .Vt uint_t
 168 bit field that is described in detail in the
 169 .Dv PRNIOC_GET_IFCAP
 170 section.
 171 Capabilities should be set one at a time;
 172 otherwise the command will return
 173 .Er EINVAL .
 174 The following capabilities can be changed by this ioctl:
 175 .Bl -tag -width PRN_BIDI
 176 .It Dv PRN_BIDI
 177 When this capability is set, the interface operates in a
 178 bidirectional mode, instead of forward-only mode.
 179 Devices that support only one
 180 mode will not return error; applications should use
 181 .Dv PRNIOC_GET_IFCAP
 182 to check if the mode was successfully changed.
 183 Because some capabilities may be
 184 altered as a side effect of changing other capabilities, this command should be
 185 followed by
 186 .Dv PRNIOC_GET_IFCAP .
 187 .El
 188 .It Dv PRNIOC_GET_IFINFO
 189 This command can be used to retrieve printer interface info string, which is an
 190 arbitrary format string usually describing the bus type.
 191 The argument is a
 192 pointer to
 193 .Vt struct prn_interface_info
 194 as described below.
 195 .Bd -literal -offset 2n
 196 struct prn_interface_info {
 197   uint_t          if_len;   /* length of buffer */
 198   uint_t          if_rlen;  /* actual info length */
 199   char   *if_data;          /* buffer address */
 200 };
 201 .Ed
 202 .Pp
 203 The application allocates a buffer and sets
 204 .Fa if_data
 205 and
 206 .Fa if_len
 207 values to its address and length, respectively.
 208 The driver returns the string
 209 to this buffer and sets
 210 .Fa if_len
 211 to its length.
 212 If
 213 .Fa if_len
 214 is less
 215 than
 216 .Fa if_rlen ,
 217 the driver must return the first
 218 .Fa if_len
 219 bytes of the string.
 220 The application may then repeat the command with a bigger buffer.
 221 .Pp
 222 Although
 223 .Nm
 224 does not limit the contents of the interface info string,
 225 some values are recommended and defined in
 226 .In sys/prnio.h
 227 by the following macros:
 228 .Pp
 229 .Bl -tag -width PRN_PARALLEL -compact
 230 .It Dv PRN_PARALLEL
 231 Centronics or
 232 .Em IEEE 1284
 233 compatible devices
 234 .It Dv PRN_SERIAL
 235 EIA-232/EIA-485 serial ports
 236 .It Dv PRN_USB
 237 Universal Serial Bus printers
 238 .It Dv PRN_1394
 239 .Em IEEE 1394
 240 peripherals
 241 .El
 242 .Pp
 243 Printer interface info string is for information only: no implications should
 244 be made from its value.
 245 .It Dv PRNIOC_RESET
 246 Some applications may want to reset the printer state during Setup and/or
 247 Cleanup phase using
 248 .Dv PRNIOC_RESET
 249 command.
 250 Reset semantics are
 251 device-specific, and in general, applications using this command should be
 252 aware of the printer type.
 253 .Pp
 254 Each
 255 .Nm
 256 compliant driver is required to accept this request, although
 257 performed actions are completely driver-dependent.
 258 More information on the
 259 .Dv PRNIOC_RESET
 260 implementation for the particular driver is available in the
 261 corresponding man page and printer manual.
 262 .It Dv PRNIOC_GET_1284_DEVID
 263 This command can be used to retrieve printer device ID as defined by
 264 .Em IEEE 1284-1994 .
 265 The
 266 .Xr ioctl 2
 267 argument is a pointer to
 268 .Vt struct prn_1284_device_id
 269 as described below.
 270 .Bd -literal -offset 2n
 271 struct prn_1284_device_id {
 272    uint_t         id_len;   /* length of buffer */
 273    uint_t         id_rlen;  /* actual ID length */
 274    char           *id_data; /* buffer address */
 275 };
 276 .Ed
 277 .Pp
 278 For convenience, the two-byte length field is not considered part of device ID
 279 string and is not returned in the user buffer.
 280 Instead,
 281 .Fa id_rlen
 282 value shall be set to (length - 2) by the driver, where length is the ID
 283 length field value.
 284 If buffer length is less than
 285 .Fa id_rlen ,
 286 the driver returns the first
 287 .Fa id_len
 288 bytes of the ID.
 289 .Pp
 290 The printer driver must return the most up-to-date value of the device ID.
 291 .It Dv PRNIOC_GET_STATUS
 292 This command can be used by applications to retrieve current device status.
 293 The argument is a pointer to
 294 .Vt uint_t ,
 295 where the status word is returned.
 296 Status is a combination of the following bits:
 297 .Bl -tag -width PRN_ONLINE
 298 .It Dv PRN_ONLINE
 299 For devices that support
 300 .Dv PRN_HOTPLUG
 301 capability, this bit is set when the device is online, otherwise the device is
 302 offline.
 303 Devices without
 304 .Dv PRN_HOTPLUG
 305 support should always have this bit set.
 306 .It Dv PRN_READY
 307 This bit indicates if the device is ready to receive/send data.
 308 Applications may use this bit for an outbound flow control.
 309 .El
 310 .It Dv PRNIOC_GET_1284_STATUS
 311 Devices that support
 312 .Dv PRN_1284_STATUS
 313 capability accept this ioctl to
 314 retrieve the device status lines defined in
 315 .Em IEEE 1284
 316 for use in Compatibility mode.
 317 The following bits may be set by the driver:
 318 .Pp
 319 .Bl -tag -width PRN_1284_NOFAULT -compact
 320 .It Dv PRN_1284_NOFAULT
 321 Device is not in error state
 322 .It Dv PRN_1284_SELECT
 323 Device is selected
 324 .It Dv PRN_1284_PE
 325 Paper error
 326 .It Dv PRN_1284_BUSY
 327 Device is busy
 328 .El
 329 .It Dv PRNIOC_GET_TIMEOUTS
 330 This command retrieves current transfer timeout values for the driver.
 331 The argument is a pointer to
 332 .Vt struct prn_timeouts
 333 as described below.
 334 .Bd -literal -offset 2n
 335 struct prn_timeouts {
 336     uint_t tmo_forward; /* forward transfer timeout */
 337     uint_t tmo_reverse; /* reverse transfer timeout */
 338 };
 339 .Ed
 340 .Pp
 341 .Fa tmo_forward
 342 and
 343 .Fa tmo_reverse
 344 define forward and reverse transfer timeouts in seconds.
 345 This command is only valid for drivers that support
 346 .Dv PRN_TIMEOUTS
 347 capability.
 348 .It Dv PRNIOC_SET_TIMEOUTS
 349 This command sets current transfer timeout values for the driver.
 350 The argument is a pointer to
 351 .Vt struct prn_timeouts .
 352 See
 353 .Sx PRNIOC_GET_TIMEOUTS
 354 for description of this structure.
 355 This command is only valid for drivers that support
 356 .Dv PRN_TIMEOUTS
 357 capability.
 358 .El
 359 .Sh SEE ALSO
 360 .Xr close 2 ,
 361 .Xr ioctl 2 ,
 362 .Xr read 2 ,
 363 .Xr write 2 ,
 364 .Xr attributes 5 ,
 365 .Xr ecpp 7D ,
 366 .Xr lp 7D ,
 367 .Xr usbprn 7D
 368 .Rs
 369 .%T IEEE Std 1284-1994
 370 .Re