Re: [PATCH v4] hwmon: (pmbus/mp2975) Fix driver initialization for MP2975 device

From: Guenter Roeck
Date: Sat Jan 27 2024 - 10:23:10 EST


On 1/27/24 01:25, Konstantin Aladyshev wrote:
The commit 1feb31e810b0 ("hwmon: (pmbus/mp2975) Simplify VOUT code")
has introduced a bug that makes it impossible to initialize MP2975
device:
"""
mp2975 5-0020: Failed to identify chip capabilities
i2c i2c-5: new_device: Instantiated device mp2975 at 0x20
i2c i2c-5: delete_device: Deleting device mp2975 at 0x20
"""
Since the 'read_byte_data' function was removed from the
'pmbus_driver_info ' structure the driver no longer reports correctly
that VOUT mode is direct. Therefore 'pmbus_identify_common' fails
with error, making it impossible to initialize the device.

Restore 'read_byte_data' function to fix the issue.

Tested:
- before: it is not possible to initialize MP2975 device with the
'mp2975' driver,
- after: 'mp2975' correctly initializes MP2975 device and all sensor
data is correct.

Fixes: 1feb31e810b0 ("hwmon: (pmbus/mp2975) Simplify VOUT code")

Signed-off-by: Konstantin Aladyshev <aladyshev22@xxxxxxxxx>
---
Changes in v4:
- Correct comment inside the 'mp2975_read_byte_data' function as
suggested by Patrick Rudolph


I already applied version 3 of the patch. Feel free to send a follow-up
to that patch. It is too late for a v4 of the original patch.

Guenter