Currently iio_debugfs_read_reg calls debugfs_reg_access
every time it is ran. Reading the same hardware register
multiple times during the same reading of a debugfs file
can cause unintended effects.
For example for each: cat iio:device0/direct_reg_access
the file_operations.read function will be called at least
twice. First will return the full length of the string in
bytes and the second will return 0.
This patch makes iio_debugfs_read_reg to call debugfs_reg_access
only when the user's buffer position (*ppos) is 0. (meaning
it is the beginning of a new reading of the debugfs file).
Fixes: e553f182d55b ("staging: iio: core: Introduce debugfs support, add support for direct register access")
Signed-off-by: Alexandru Tachici <alexandru.tachici@xxxxxxxxxx>
---
drivers/iio/industrialio-core.c | 34 +++++++++++++++++++++++----------
include/linux/iio/iio.h | 2 ++
2 files changed, 26 insertions(+), 10 deletions(-)
diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
index 65ff0d067018..637cea14afdb 100644
--- a/drivers/iio/industrialio-core.c
+++ b/drivers/iio/industrialio-core.c
@@ -297,26 +297,40 @@ static void __exit iio_exit(void)
}
#if defined(CONFIG_DEBUG_FS)
-static ssize_t iio_debugfs_read_reg(struct file *file, char __user *userbuf,
- size_t count, loff_t *ppos)
+static int iio_debugfs_get_reg_string(struct iio_dev *indio_dev)
{
- struct iio_dev *indio_dev = file->private_data;
- char buf[20];
+ const struct iio_info *info = indio_dev->info;
unsigned val = 0;
- ssize_t len;
int ret;
- ret = indio_dev->info->debugfs_reg_access(indio_dev,
- indio_dev->cached_reg_addr,
- 0, &val);
+ ret = info->debugfs_reg_access(indio_dev, indio_dev->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);
+ return 0;
+}
- len = snprintf(buf, sizeof(buf), "0x%X\n", val);
+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;
+ loff_t pos = *ppos;
+ int ret;
+
+ if (pos == 0) {
+ ret = iio_debugfs_get_reg_string(indio_dev);
+ if (ret)
+ return ret;
+ }
- return simple_read_from_buffer(userbuf, count, ppos, buf, len);
+ return simple_read_from_buffer(userbuf, count, ppos,
+ indio_dev->read_buf,
+ indio_dev->read_buf_len);
}
static ssize_t iio_debugfs_write_reg(struct file *file,
diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
index 862ce0019eba..eed58ed2f368 100644
--- a/include/linux/iio/iio.h
+++ b/include/linux/iio/iio.h
@@ -568,6 +568,8 @@ struct iio_dev {
#if defined(CONFIG_DEBUG_FS)
struct dentry *debugfs_dentry;
unsigned cached_reg_addr;
+ char read_buf[20];
+ unsigned int read_buf_len;
#endif
};
--
2.20.1
