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

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Message-ID: <33da3135-4450-4c5e-92af-0d361c3b7489@roeck-us.net>
Date: Sat, 27 Jan 2024 07:22:56 -0800
From: Guenter Roeck <linux@...ck-us.net>
To: Konstantin Aladyshev <aladyshev22@...il.com>
Cc: Jean Delvare <jdelvare@...e.com>,
 Naresh Solanki <Naresh.Solanki@...ements.com>,
 Patrick Rudolph <patrick.rudolph@...ements.com>,
 linux-hwmon@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] hwmon: (pmbus/mp2975) Fix driver initialization for
 MP2975 device

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@...il.com>
> ---
> 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