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authorAlexandru Tachici <alexandru.tachici@analog.com>2020-02-21 15:06:55 +0300
committerJonathan Cameron <Jonathan.Cameron@huawei.com>2020-03-08 20:28:51 +0300
commit2ddc982a6c172c141183ac954d44f01bc4f2fe72 (patch)
treef8b0879d2807b3b55bbbc7d6c34bd1973182dcd9 /drivers/iio/industrialio-core.c
parent2303248b291f537f0414a644a53483c71023136f (diff)
downloadlinux-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.c15
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,