iio: industrialio-core: Fix debugfs read
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: e553f182d5
("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>
This commit is contained in:
parent
2303248b29
commit
2ddc982a6c
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@ -301,11 +301,14 @@ static ssize_t iio_debugfs_read_reg(struct file *file, char __user *userbuf,
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size_t count, loff_t *ppos)
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{
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struct iio_dev *indio_dev = file->private_data;
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char buf[20];
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unsigned val = 0;
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ssize_t len;
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int ret;
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if (*ppos > 0)
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return simple_read_from_buffer(userbuf, count, ppos,
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indio_dev->read_buf,
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indio_dev->read_buf_len);
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ret = indio_dev->info->debugfs_reg_access(indio_dev,
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indio_dev->cached_reg_addr,
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0, &val);
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@ -314,9 +317,13 @@ static ssize_t iio_debugfs_read_reg(struct file *file, char __user *userbuf,
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return ret;
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}
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len = snprintf(buf, sizeof(buf), "0x%X\n", val);
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indio_dev->read_buf_len = snprintf(indio_dev->read_buf,
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sizeof(indio_dev->read_buf),
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"0x%X\n", val);
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return simple_read_from_buffer(userbuf, count, ppos, buf, len);
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return simple_read_from_buffer(userbuf, count, ppos,
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indio_dev->read_buf,
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indio_dev->read_buf_len);
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}
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static ssize_t iio_debugfs_write_reg(struct file *file,
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@ -568,6 +568,8 @@ struct iio_dev {
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#if defined(CONFIG_DEBUG_FS)
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struct dentry *debugfs_dentry;
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unsigned cached_reg_addr;
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char read_buf[20];
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unsigned int read_buf_len;
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#endif
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};
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