iio: core: move debugfs data on the private iio dev info

This change moves all iio_dev debugfs fields to the iio_dev_priv object.
It's not the biggest advantage yet (to the whole thing of abstractization)
but it's a start.

The iio_get_debugfs_dentry() function (which is moved in
industrialio-core.c) needs to also be guarded against the CONFIG_DEBUG_FS
symbol, when it isn't defined. We do want to keep the inline definition in
the iio.h header, so that the compiler can better infer when to compile out
debugfs code that is related to the IIO debugfs directory.

Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/industrialio-core.c

@@ -165,6 +165,19 @@ static const char * const iio_chan_info_postfix[] = {
 	[IIO_CHAN_INFO_THERMOCOUPLE_TYPE] = "thermocouple_type",
 };
 
+#if defined(CONFIG_DEBUG_FS)
+/**
+ * There's also a CONFIG_DEBUG_FS guard in include/linux/iio/iio.h for
+ * iio_get_debugfs_dentry() to make it inline if CONFIG_DEBUG_FS is undefined
+ */
+struct dentry *iio_get_debugfs_dentry(struct iio_dev *indio_dev)
+{
+	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
+	return iio_dev_opaque->debugfs_dentry;
+}
+EXPORT_SYMBOL_GPL(iio_get_debugfs_dentry);
+#endif
+
 /**
  * iio_find_channel_from_si() - get channel from its scan index
  * @indio_dev:		device
@@ -308,35 +321,37 @@ static ssize_t iio_debugfs_read_reg(struct file *file, char __user *userbuf,
 			      size_t count, loff_t *ppos)
 {
 	struct iio_dev *indio_dev = file->private_data;
+	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
 	unsigned val = 0;
 	int ret;
 
 	if (*ppos > 0)
 		return simple_read_from_buffer(userbuf, count, ppos,
-					       indio_dev->read_buf,
-					       indio_dev->read_buf_len);
+					       iio_dev_opaque->read_buf,
+					       iio_dev_opaque->read_buf_len);
 
 	ret = indio_dev->info->debugfs_reg_access(indio_dev,
-						  indio_dev->cached_reg_addr,
+						  iio_dev_opaque->cached_reg_addr,
 						  0, &val);
 	if (ret) {
 		dev_err(indio_dev->dev.parent, "%s: read failed\n", __func__);
 		return ret;
 	}
 
-	indio_dev->read_buf_len = snprintf(indio_dev->read_buf,
-					   sizeof(indio_dev->read_buf),
-					   "0x%X\n", val);
+	iio_dev_opaque->read_buf_len = snprintf(iio_dev_opaque->read_buf,
+					      sizeof(iio_dev_opaque->read_buf),
+					      "0x%X\n", val);
 
 	return simple_read_from_buffer(userbuf, count, ppos,
-				       indio_dev->read_buf,
-				       indio_dev->read_buf_len);
+				       iio_dev_opaque->read_buf,
+				       iio_dev_opaque->read_buf_len);
 }
 
 static ssize_t iio_debugfs_write_reg(struct file *file,
 		     const char __user *userbuf, size_t count, loff_t *ppos)
 {
 	struct iio_dev *indio_dev = file->private_data;
+	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
 	unsigned reg, val;
 	char buf[80];
 	int ret;
@@ -351,10 +366,10 @@ static ssize_t iio_debugfs_write_reg(struct file *file,
 
 	switch (ret) {
 	case 1:
-		indio_dev->cached_reg_addr = reg;
+		iio_dev_opaque->cached_reg_addr = reg;
 		break;
 	case 2:
-		indio_dev->cached_reg_addr = reg;
+		iio_dev_opaque->cached_reg_addr = reg;
 		ret = indio_dev->info->debugfs_reg_access(indio_dev, reg,
 							  val, NULL);
 		if (ret) {
@@ -378,23 +393,28 @@ static const struct file_operations iio_debugfs_reg_fops = {
 
 static void iio_device_unregister_debugfs(struct iio_dev *indio_dev)
 {
-	debugfs_remove_recursive(indio_dev->debugfs_dentry);
+	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
+	debugfs_remove_recursive(iio_dev_opaque->debugfs_dentry);
 }
 
 static void iio_device_register_debugfs(struct iio_dev *indio_dev)
 {
+	struct iio_dev_opaque *iio_dev_opaque;
+
 	if (indio_dev->info->debugfs_reg_access == NULL)
 		return;
 
 	if (!iio_debugfs_dentry)
 		return;
 
-	indio_dev->debugfs_dentry =
+	iio_dev_opaque = to_iio_dev_opaque(indio_dev);
+
+	iio_dev_opaque->debugfs_dentry =
 		debugfs_create_dir(dev_name(&indio_dev->dev),
 				   iio_debugfs_dentry);
 
 	debugfs_create_file("direct_reg_access", 0644,
-			    indio_dev->debugfs_dentry, indio_dev,
+			    iio_dev_opaque->debugfs_dentry, indio_dev,
 			    &iio_debugfs_reg_fops);
 }
 #else

include/linux/iio/iio-opaque.h

@@ -6,9 +6,19 @@
 /**
  * struct iio_dev_opaque - industrial I/O device opaque information
  * @indio_dev:			public industrial I/O device information
+ * @debugfs_dentry:		device specific debugfs dentry
+ * @cached_reg_addr:		cached register address for debugfs reads
+ * @read_buf:			read buffer to be used for the initial reg read
+ * @read_buf_len:		data length in @read_buf
  */
 struct iio_dev_opaque {
 	struct iio_dev			indio_dev;
+#if defined(CONFIG_DEBUG_FS)
+	struct dentry			*debugfs_dentry;
+	unsigned			cached_reg_addr;
+	char				read_buf[20];
+	unsigned int			read_buf_len;
+#endif
 };
 
 #define to_iio_dev_opaque(indio_dev)		\

include/linux/iio/iio.h

@@ -520,8 +520,6 @@ struct iio_buffer_setup_ops {
  * @groups:		[INTERN] attribute groups
  * @groupcounter:	[INTERN] index of next attribute group
  * @flags:		[INTERN] file ops related flags including busy flag.
- * @debugfs_dentry:	[INTERN] device specific debugfs dentry.
- * @cached_reg_addr:	[INTERN] cached register address for debugfs reads.
  * @priv:		[DRIVER] reference to driver's private information
  *			**MUST** be accessed **ONLY** via iio_priv() helper
  */
@@ -567,12 +565,6 @@ struct iio_dev {
 	int				groupcounter;
 
 	unsigned long			flags;
-#if defined(CONFIG_DEBUG_FS)
-	struct dentry			*debugfs_dentry;
-	unsigned			cached_reg_addr;
-	char				read_buf[20];
-	unsigned int			read_buf_len;
-#endif
 	void				*priv;
 };
 
@@ -733,10 +725,7 @@ static inline bool iio_buffer_enabled(struct iio_dev *indio_dev)
  * @indio_dev:		IIO device structure for device
  **/
 #if defined(CONFIG_DEBUG_FS)
-static inline struct dentry *iio_get_debugfs_dentry(struct iio_dev *indio_dev)
-{
-	return indio_dev->debugfs_dentry;
-}
+struct dentry *iio_get_debugfs_dentry(struct iio_dev *indio_dev);
 #else
 static inline struct dentry *iio_get_debugfs_dentry(struct iio_dev *indio_dev)
 {