staging: comedi: core: introduce comedi_dio_insn_config()

DIO subdevices always handle the INSN_CONFIG_DIO_{INPUT,OUTPUT} instructions
to configure the dio channels. They also always handle the INSN_CONFIG_DIO_QUERY
instruction to query the configuration of a dio channel.

Introduce a helper function to handle the (*insn_config) boilerplate for
comedi DIO subdevices. This function has the same parameters as (*insn_config)
functions with an additional parameter to allow the caller to pass a 'mask'
value for grouped dio channels.

This function returns:

  0 if the instruction was successful but requires additional handling by
  the caller (INSN_CONFIG_DIO_{INPUT,OUTPUT}

  insn->n if the instruction was handled (INSN_CONFIG_DIO_QUERY)

  -EINVAL for all unhandled instructions

The caller is responsible for actually configuring the hardware based on
the configuration (s->io_bits).
Signed-off-by: NH Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: NIan Abbott <abbotti@mev.co.uk>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/comedidev.h

@@ -342,6 +342,10 @@ void comedi_buf_memcpy_from(struct comedi_async *async, unsigned int offset,
 
 /* drivers.c - general comedi driver functions */
 
+int comedi_dio_insn_config(struct comedi_device *, struct comedi_subdevice *,
+			   struct comedi_insn *, unsigned int *data,
+			   unsigned int mask);
+
 void *comedi_alloc_devpriv(struct comedi_device *, size_t);
 int comedi_alloc_subdevices(struct comedi_device *, int);
 

drivers/staging/comedi/drivers.c

@@ -150,6 +150,46 @@ int insn_inval(struct comedi_device *dev, struct comedi_subdevice *s,
 	return -EINVAL;
 }
 
+/**
+ * comedi_dio_insn_config() - boilerplate (*insn_config) for DIO subdevices.
+ * @dev: comedi_device struct
+ * @s: comedi_subdevice struct
+ * @insn: comedi_insn struct
+ * @data: parameters for the @insn
+ * @mask: io_bits mask for grouped channels
+ */
+int comedi_dio_insn_config(struct comedi_device *dev,
+			   struct comedi_subdevice *s,
+			   struct comedi_insn *insn,
+			   unsigned int *data,
+			   unsigned int mask)
+{
+	unsigned int chan_mask = 1 << CR_CHAN(insn->chanspec);
+
+	if (!mask)
+		mask = chan_mask;
+
+	switch (data[0]) {
+	case INSN_CONFIG_DIO_INPUT:
+		s->io_bits &= ~mask;
+		break;
+
+	case INSN_CONFIG_DIO_OUTPUT:
+		s->io_bits |= mask;
+		break;
+
+	case INSN_CONFIG_DIO_QUERY:
+		data[1] = (s->io_bits & mask) ? COMEDI_OUTPUT : COMEDI_INPUT;
+		return insn->n;
+
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(comedi_dio_insn_config);
+
 static int insn_rw_emulate_bits(struct comedi_device *dev,
 				struct comedi_subdevice *s,
 				struct comedi_insn *insn, unsigned int *data)