Explicitly disable PEC when the client does not support it.
The problematic scenario is the following. A device with enabled PEC
support is up and running and a kernel driver is loaded.
Then the driver is unloaded (or device unbound), the HW device
is reconfigured externally (e.g. by i2cset) to advertise itself as not
supporting PEC. Without a new code, at the second load of the driver
(or bind) the "flags" variable is not updated to avoid PEC usage. As a
consequence the further communication with the device is done with
the PEC enabled, which is wrong and may fail.
The implementation first disable the I2C_CLIENT_PEC flag, then the old
code enable it if needed.
Signed-off-by: Adam Wujek <dev_public@xxxxxxxx>
---
Notes:
Changes in v2:
- Rebase to the latest kernel
- Update commit message
Changes in v3:
- Rework the patch, disable the flag first, then enable if needed.
Adding three else statements to disable the flag will make the code
less readable.
- Update commit message
drivers/hwmon/pmbus/pmbus_core.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c
index b2618b1d529e..d93574d6a1fb 100644
--- a/drivers/hwmon/pmbus/pmbus_core.c
+++ b/drivers/hwmon/pmbus/pmbus_core.c
@@ -2326,6 +2326,9 @@ static int pmbus_init_common(struct i2c_client *client, struct pmbus_data *data,
data->has_status_word = true;
}
+ /* Make sure PEC is disabled, will be enabled later if needed */
+ client->flags &= ~I2C_CLIENT_PEC;
+
/* Enable PEC if the controller and bus supports it */
if (!(data->flags & PMBUS_NO_CAPABILITY)) {
ret = i2c_smbus_read_byte_data(client, PMBUS_CAPABILITY);
--
2.25.1
