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| author | Alexandru Tachici <alexandru.tachici@analog.com> | 2020-02-21 15:06:55 +0300 |
|---|---|---|
| committer | Jonathan Cameron <Jonathan.Cameron@huawei.com> | 2020-03-08 20:28:51 +0300 |
| commit | 2ddc982a6c172c141183ac954d44f01bc4f2fe72 (patch) | |
| tree | f8b0879d2807b3b55bbbc7d6c34bd1973182dcd9 /drivers/iio/industrialio-core.c | |
| parent | 2303248b291f537f0414a644a53483c71023136f (diff) | |
| download | linux-2ddc982a6c172c141183ac954d44f01bc4f2fe72.tar.xz | |
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: e553f182d55b ("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>
Diffstat (limited to 'drivers/iio/industrialio-core.c')
| -rw-r--r-- | drivers/iio/industrialio-core.c | 15 |
1 files changed, 11 insertions, 4 deletions
diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c index 0b14666dff09..eac63c1bb8da 100644 --- a/drivers/iio/industrialio-core.c +++ b/drivers/iio/industrialio-core.c @@ -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, |