iio: inkern: Add of_xlate function to struct iio_info

When #iio-cells is greater than '0', the driver could provide
a custom of_xlate function that reads the *args* and returns
the appropriate index in registered IIO channels array.

Add simple translation function, suitable for the most 1:1
mapped channels in IIO chips, and use it when driver did not
provide custom implementation.

Signed-off-by: Ivan T. Ivanov <iivanov@mm-sol.com>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

2 files changed, 36 insertions, 5 deletions

diff --git a/drivers/iio/inkern.c b/drivers/iio/inkern.c
index c7497009d60a..0cc505d98686 100644
--- a/drivers/iio/inkern.c
+++ b/drivers/iio/inkern.c
@@ -100,6 +100,28 @@ static int iio_dev_node_match(struct device *dev, void *data)
         return dev->of_node == data && dev->type == &iio_device_type;
 }
 
+/**
+ * __of_iio_simple_xlate - translate iiospec to the IIO channel index
+ * @indio_dev:  pointer to the iio_dev structure
+ * @iiospec:    IIO specifier as found in the device tree
+ *
+ * This is simple translation function, suitable for the most 1:1 mapped
+ * channels in IIO chips. This function performs only one sanity check:
+ * whether IIO index is less than num_channels (that is specified in the
+ * iio_dev).
+ */
+static int __of_iio_simple_xlate(struct iio_dev *indio_dev,
+                                const struct of_phandle_args *iiospec)
+{
+        if (!iiospec->args_count)
+                return 0;
+
+        if (iiospec->args[0] >= indio_dev->num_channels)
+                return -EINVAL;
+
+        return iiospec->args[0];
+}
+
 static int __of_iio_channel_get(struct iio_channel *channel,
                                 struct device_node *np, int index)
 {
@@ -122,18 +144,19 @@ static int __of_iio_channel_get(struct iio_channel *channel,
 
         indio_dev = dev_to_iio_dev(idev);
         channel->indio_dev = indio_dev;
-        index = iiospec.args_count ? iiospec.args[0] : 0;
-        if (index >= indio_dev->num_channels) {
-                err = -EINVAL;
+        if (indio_dev->info->of_xlate)
+                index = indio_dev->info->of_xlate(indio_dev, &iiospec);
+        else
+                index = __of_iio_simple_xlate(indio_dev, &iiospec);
+        if (index < 0)
                 goto err_put;
-        }
         channel->channel = &indio_dev->channels[index];
 
         return 0;
 
 err_put:
         iio_device_put(indio_dev);
-        return err;
+        return index;
 }
 
 static struct iio_channel *of_iio_channel_get(struct device_node *np, int index)
diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
index 15dc6bc2bdd2..3642ce7ef512 100644
--- a/include/linux/iio/iio.h
+++ b/include/linux/iio/iio.h
@@ -13,6 +13,7 @@
 #include <linux/device.h>
 #include <linux/cdev.h>
 #include <linux/iio/types.h>
+#include <linux/of.h>
 /* IIO TODO LIST */
 /*
  * Provide means of adjusting timer accuracy.
@@ -326,6 +327,11 @@ struct iio_dev;
  * @update_scan_mode:   function to configure device and scan buffer when
  *                      channels have changed
  * @debugfs_reg_access: function to read or write register value of device
+ * @of_xlate:           function pointer to obtain channel specifier index.
+ *                      When #iio-cells is greater than '0', the driver could
+ *                      provide a custom of_xlate function that reads the
+ *                      *args* and returns the appropriate index in registered
+ *                      IIO channels array.
  **/
 struct iio_info {
         struct module                   *driver_module;
@@ -385,6 +391,8 @@ struct iio_info {
         int (*debugfs_reg_access)(struct iio_dev *indio_dev,
                                   unsigned reg, unsigned writeval,
                                   unsigned *readval);
+        int (*of_xlate)(struct iio_dev *indio_dev,
+                        const struct of_phandle_args *iiospec);
 };
 
 /**