BSP and Device Driver Development Guide
This corresponds to the driver write call. After validating the minor number and arguments, this call writes the indicated device. If the specified device is an ADC, then an error is usually returned.
The value written is an unsigned32 number
representing the value to be written to the specified
bitfield. This value is stored in the
argument_block passed in to the call.
NOTE: Some discrete I/O drivers have a special minor number
used to access all discrete I/O bits on the board. If this special
minor is used, then the area pointed to by argument_block must
be the correct size.
BSP and Device Driver Development Guide
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