linux-kernel - Re: [PATCH] hwmod: (pmbus) disable PEC if not enabled

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Message-ID: <734e748b-941c-5ae1-5140-22cc845bdfc1@roeck-us.net>
Date:   Tue, 19 Apr 2022 15:00:19 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Adam Wujek <dev_public@...ek.eu>
Cc:     Jean Delvare <jdelvare@...e.com>, linux-hwmon@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] hwmod: (pmbus) disable PEC if not enabled

On 4/19/22 13:53, Adam Wujek wrote:
> Explicitly disable PEC when the client does not support it.
> Without the explicit disable, when the device with the PEC support is removed
> later when a device without PEC support is inserted into the same address,
> the driver uses the old value of client->flags which contains the I2C_CLIENT_PEC
> flag. As a consequence the PEC is used when it should not.
> 

How can that happen ? I would assume the I2C device gets deleted and re-created
in that case, which should clear the PEC flag.

Guenter

> Signed-off-by: Adam Wujek <dev_public@...ek.eu>
> ---
>   drivers/hwmon/pmbus/pmbus_core.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c
> index 82c3754e21e3..f8ca36759b0a 100644
> --- a/drivers/hwmon/pmbus/pmbus_core.c
> +++ b/drivers/hwmon/pmbus/pmbus_core.c
> @@ -2014,6 +2014,8 @@ static int pmbus_init_common(struct i2c_client *client, struct pmbus_data *data,
>   	ret = i2c_smbus_read_byte_data(client, PMBUS_CAPABILITY);
>   	if (ret >= 0 && (ret & PB_CAPABILITY_ERROR_CHECK))
>   		client->flags |= I2C_CLIENT_PEC;
> +	else
> +		client->flags &= ~I2C_CLIENT_PEC;
> 
>   	pmbus_clear_faults(client);
> 
> --
> 2.17.1
> 
>