iio: industrialio-core: Fix debugfs read (2ddc982a) · Commits · 戴 / test

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: ("staging: iio: core: Introduce debugfs support, add support for direct register access") Signed-off-by:

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

Alexandru Tachici <alexandru.tachici@analog.com> Signed-off-by:

Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/industrialio-core.c

+11 −4

Original line number	Diff line number	Diff line
		@@ -301,11 +301,14 @@ 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;
		char buf[20];
		unsigned val = 0;
		ssize_t len;
		int ret;

		if (*ppos > 0)
		return simple_read_from_buffer(userbuf, count, ppos,
		indio_dev->read_buf,
		indio_dev->read_buf_len);

		ret = indio_dev->info->debugfs_reg_access(indio_dev,
		indio_dev->cached_reg_addr,
		0, &val);
		@@ -314,9 +317,13 @@ static ssize_t iio_debugfs_read_reg(struct file file, char __user userbuf,
		return ret;
		}

		len = snprintf(buf, sizeof(buf), "0x%X\n", val);
		indio_dev->read_buf_len = snprintf(indio_dev->read_buf,
		sizeof(indio_dev->read_buf),
		"0x%X\n", val);

		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,

include/linux/iio/iio.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -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
		};

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