linux-kernel - Re: [PATCH v2] i2c: busses: i2c-cadence: fix message length when receive block message

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Date:   Tue, 24 May 2022 17:05:54 +0200
From:   Michal Simek <michal.simek@...inx.com>
To:     Adam Wujek <dev_public@...ek.eu>,
        Shubhrajyoti Datta <shubhrajyoti.datta@...inx.com>
CC:     Michal Simek <michal.simek@...inx.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-i2c@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] i2c: busses: i2c-cadence: fix message length when
 receive block message



On 5/20/22 01:11, Adam Wujek wrote:
> Needed by hwmon/pmbus_core driver to calculate PEC correctly.
> The hwmon/pmbus_core driver relies on bus drivers to update the message
> length of receive block transfers. Only in this type of smbus transfer
> the length is not known before the transfer is started.
> 
> Signed-off-by: Adam Wujek <dev_public@...ek.eu>
> ---
> Notes:
>      Changes in v2:
>      - fix multiline comment
> 
>   drivers/i2c/busses/i2c-cadence.c | 7 +++++++
>   1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/i2c/busses/i2c-cadence.c b/drivers/i2c/busses/i2c-cadence.c
> index 805c77143a0f..a679eb390ef5 100644
> --- a/drivers/i2c/busses/i2c-cadence.c
> +++ b/drivers/i2c/busses/i2c-cadence.c
> @@ -794,6 +794,13 @@ static int cdns_i2c_process_msg(struct cdns_i2c *id, struct i2c_msg *msg,
>   		return -ETIMEDOUT;
>   	}
> 
> +	/*
> +	 * Update message len, as i2c/smbus driver (function
> +	 * i2c_smbus_xfer_emulated) relies on i2c device drivers to do this.
> +	 */
> +	if ((msg->flags & I2C_M_RECV_LEN) && (msg->flags & I2C_M_RD))
> +		msg->len = msg->buf[0] + 2; /* add len byte + PEC byte */
> +
>   	cdns_i2c_writereg(CDNS_I2C_IXR_ALL_INTR_MASK,
>   			  CDNS_I2C_IDR_OFFSET);
> 
> --
> 2.17.1
> 
> 

Shubhrajyoti: Can you please test it?

Thanks,
Michal