From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pontus Andersson Subject: [PATCH] i2c: ismt: Separate I2C block read from SMBus block read Date: Mon, 2 Oct 2017 14:45:19 +0200 Message-ID: <20171002124519.GA13496@leonis.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mail-lf0-f67.google.com ([209.85.215.67]:38517 "EHLO mail-lf0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750929AbdJBMpY (ORCPT ); Mon, 2 Oct 2017 08:45:24 -0400 Content-Disposition: inline Sender: linux-i2c-owner@vger.kernel.org List-Id: linux-i2c@vger.kernel.org To: Seth Heasley , Neil Horman , Wolfram Sang , linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org Commit b6c159a9cb69 ("i2c: ismt: Don't duplicate the receive length for block reads") broke I2C block reads. It aimed to fix normal SMBus block read, but changed the correct behavior of I2C block read in the process. According to Documentation/i2c/smbus-protocol, one vital difference between normal SMBus block read and I2C block read is that there is no byte count prefixed in the data sent on the wire: SMBus Block Read: i2c_smbus_read_block_data() S Addr Wr [A] Comm [A] S Addr Rd [A] [Count] A [Data] A [Data] A ... A [Data] NA P I2C Block Read: i2c_smbus_read_i2c_block_data() S Addr Wr [A] Comm [A] S Addr Rd [A] [Data] A [Data] A ... A [Data] NA P Therefore the two transaction types need to be processed differently in the driver by copying of the dma_buffer as done previously for the I2C_SMBUS_I2C_BLOCK_DATA case. Fixes: b6c159a9cb69 ("i2c: ismt: Don't duplicate the receive length for block reads") Signed-off-by: Pontus Andersson Cc: stable@vger.kernel.org --- drivers/i2c/busses/i2c-ismt.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/drivers/i2c/busses/i2c-ismt.c b/drivers/i2c/busses/i2c-ismt.c index 22ffcb73c185..b51adffa4841 100644 --- a/drivers/i2c/busses/i2c-ismt.c +++ b/drivers/i2c/busses/i2c-ismt.c @@ -340,12 +340,15 @@ static int ismt_process_desc(const struct ismt_desc *desc, data->word = dma_buffer[0] | (dma_buffer[1] << 8); break; case I2C_SMBUS_BLOCK_DATA: - case I2C_SMBUS_I2C_BLOCK_DATA: if (desc->rxbytes != dma_buffer[0] + 1) return -EMSGSIZE; memcpy(data->block, dma_buffer, desc->rxbytes); break; + case I2C_SMBUS_I2C_BLOCK_DATA: + memcpy(&data->block[1], dma_buffer, desc->rxbytes); + data->block[0] = desc->rxbytes; + break; } return 0; } -- 2.14.1