#define COMEDI_NUM_BOARD_MINORS 0x30
+/**
+ * struct comedi_subdevice - Working data for a COMEDI subdevice
+ * @device: COMEDI device to which this subdevice belongs. (Initialized by
+ * comedi_alloc_subdevices().)
+ * @index: Index of this subdevice within device's array of subdevices.
+ * (Initialized by comedi_alloc_subdevices().)
+ * @type: Type of subdevice from &enum comedi_subdevice_type. (Initialized by
+ * the low-level driver.)
+ * @n_chan: Number of channels the subdevice supports. (Initialized by the
+ * low-level driver.)
+ * @subdev_flags: Various "SDF" flags indicating aspects of the subdevice to
+ * the COMEDI core and user application. (Initialized by the low-level
+ * driver.)
+ * @len_chanlist: Maximum length of a channel list if the subdevice supports
+ * asynchronous acquisition commands. (Optionally initialized by the
+ * low-level driver, or changed from 0 to 1 during post-configuration.)
+ * @private: Private data pointer which is either set by the low-level driver
+ * itself, or by a call to comedi_alloc_spriv() which allocates storage.
+ * In the latter case, the storage is automatically freed after the
+ * low-level driver's "detach" handler is called for the device.
+ * (Initialized by the low-level driver.)
+ * @async: Pointer to &struct comedi_async id the subdevice supports
+ * asynchronous acquisition commands. (Allocated and initialized during
+ * post-configuration if needed.)
+ * @lock: Pointer to a file object that performed a %COMEDI_LOCK ioctl on the
+ * subdevice. (Initially NULL.)
+ * @busy: Pointer to a file object that is performing an asynchronous
+ * acquisition command on the subdevice. (Initially NULL.)
+ * @runflags: Internal flags for use by COMEDI core, mostly indicating whether
+ * an asynchronous acquisition command is running.
+ * @spin_lock: Generic spin-lock for use by the COMEDI core and the low-level
+ * driver. (Initialized by comedi_alloc_subdevices().)
+ * @io_bits: Bit-mask indicating the channel directions for a DIO subdevice
+ * with no more than 32 channels. A '1' at a bit position indicates the
+ * corresponding channel is configured as an output. (Initialized by the
+ * low-level driver for a DIO subdevice. Forced to all-outputs during
+ * post-configuration for a digital output subdevice.)
+ * @maxdata: If non-zero, this is the maximum raw data value of each channel.
+ * If zero, the maximum data value is channel-specific. (Initialized by
+ * the low-level driver.)
+ * @maxdata_list: If the maximum data value is channel-specific, this points
+ * to an array of maximum data values indexed by channel index.
+ * (Initialized by the low-level driver.)
+ * @range_table: If non-NULL, this points to a COMEDI range table for the
+ * subdevice. If NULL, the range table is channel-specific. (Initialized
+ * by the low-level driver, will be set to an "invalid" range table during
+ * post-configuration if @range_table and @range_table_list are both
+ * NULL.)
+ * @range_table_list: If the COMEDI range table is channel-specific, this
+ * points to an array of pointers to COMEDI range tables indexed by
+ * channel number. (Initialized by the low-level driver.)
+ * @chanlist: Not used.
+ * @insn_read: Optional pointer to a handler for the %INSN_READ instruction.
+ * (Initialized by the low-level driver, or set to a default handler
+ * during post-configuration.)
+ * @insn_write: Optional pointer to a handler for the %INSN_WRITE instruction.
+ * (Initialized by the low-level driver, or set to a default handler
+ * during post-configuration.)
+ * @insn_bits: Optional pointer to a handler for the %INSN_BITS instruction
+ * for a digital input, digital output or digital input/output subdevice.
+ * (Initialized by the low-level driver, or set to a default handler
+ * during post-configuration.)
+ * @insn_config: Optional pointer to a handler for the %INSN_CONFIG
+ * instruction. (Initialized by the low-level driver, or set to a default
+ * handler during post-configuration.)
+ * @do_cmd: If the subdevice supports asynchronous acquisition commands, this
+ * points to a handler to set it up in hardware. (Initialized by the
+ * low-level driver.)
+ * @do_cmdtest: If the subdevice supports asynchronous acquisition commands,
+ * this points to a handler used to check and possibly tweak a prospective
+ * acquisition command without setting it up in hardware. (Initialized by
+ * the low-level driver.)
+ * @poll: If the subdevice supports asynchronous acquisition commands, this
+ * is an optional pointer to a handler for the %COMEDI_POLL ioctl which
+ * instructs the low-level driver to synchronize buffers. (Initialized by
+ * the low-level driver if needed.)
+ * @cancel: If the subdevice supports asynchronous acquisition commands, this
+ * points to a handler used to terminate a running command. (Initialized
+ * by the low-level driver.)
+ * @buf_change: If the subdevice supports asynchronous acquisition commands,
+ * this is an optional pointer to a handler that is called when the data
+ * buffer for handling asynchronous commands is allocated or reallocated.
+ * (Initialized by the low-level driver if needed.)
+ * @munge: If the subdevice supports asynchronous acquisition commands and
+ * uses DMA to transfer data from the hardware to the acquisition buffer,
+ * this points to a function used to "munge" the data values from the
+ * hardware into the format expected by COMEDI. (Initialized by the
+ * low-level driver if needed.)
+ * @async_dma_dir: If the subdevice supports asynchronous acquisition commands
+ * and uses DMA to transfer data from the hardware to the acquisition
+ * buffer, this sets the DMA direction for the buffer. (initialized to
+ * %DMA_NONE by comedi_alloc_subdevices() and changed by the low-level
+ * driver if necessary.)
+ * @state: Handy bit-mask indicating the output states for a DIO or digital
+ * output subdevice with no more than 32 channels. (Initialized by the
+ * low-level driver.)
+ * @class_dev: If the subdevice supports asynchronous acquisition commands,
+ * this points to a sysfs comediX_subdY device where X is the minor device
+ * number of the COMEDI device and Y is the subdevice number. The minor
+ * device number for the sysfs device is allocated dynamically in the
+ * range 48 to 255. This is used to allow the COMEDI device to be opened
+ * with a different default read or write subdevice. (Allocated during
+ * post-configuration if needed.)
+ * @minor: If @class_dev is set, this is its dynamically allocated minor
+ * device number. (Set during post-configuration if necessary.)
+ * @readback: Optional pointer to memory allocated by
+ * comedi_alloc_subdev_readback() used to hold the values written to
+ * analog output channels so they can be read back. The storage is
+ * automatically freed after the low-level driver's "detach" handler is
+ * called for the device. (Initialized by the low-level driver.)
+ *
+ * This is the main control structure for a COMEDI subdevice. If the subdevice
+ * supports asynchronous acquisition commands, additional information is stored
+ * in the &struct comedi_async pointed to by @async.
+ *
+ * Most of the subdevice is initialized by the low-level driver's "attach" or
+ * "auto_attach" handlers but parts of it are initialized by
+ * comedi_alloc_subdevices(), and other parts are initialized during
+ * post-configuration on return from that handler.
+ *
+ * A low-level driver that sets @insn_bits for a digital input, digital output,
+ * or DIO subdevice may leave @insn_read and @insn_write uninitialized, in
+ * which case they will be set to a default handler during post-configuration
+ * that uses @insn_bits to emulate the %INSN_READ and %INSN_WRITE instructions.
+ */
struct comedi_subdevice {
struct comedi_device *device;
int index;
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