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

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Message-ID: <20220519231058.437365-1-dev_public@wujek.eu>
Date:   Thu, 19 May 2022 23:11:23 +0000
From:   Adam Wujek <dev_public@...ek.eu>
To:     unlisted-recipients:; (no To-header on input)
Cc:     Adam Wujek <dev_public@...ek.eu>,
        Michal Simek <michal.simek@...inx.com>,
        linux-arm-kernel@...ts.infradead.org, linux-i2c@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2] i2c: busses: i2c-cadence: fix message length when receive block message

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