linux-kernel - RE: [RFC PATCH 1/2] i2c: mlxcpld: check correct size of maximum RECV

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Message-ID: <AM6PR05MB61688309AFCF832CA4D67696D9910@AM6PR05MB6168.eurprd05.prod.outlook.com>
Date:   Sun, 28 Jun 2020 13:50:14 +0000
From:   Michael Shych <michaelsh@...lanox.com>
To:     Wolfram Sang <wsa+renesas@...g-engineering.com>,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>
CC:     "linux-renesas-soc@...r.kernel.org" 
        <linux-renesas-soc@...r.kernel.org>,
        Vadim Pasternak <vadimp@...lanox.com>,
        Wolfram Sang <wsa@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [RFC PATCH 1/2] i2c: mlxcpld: check correct size of maximum
 RECV_LEN packet

Hi Wolfram,

You are right, +1 isn't required.
Checked your patch also on HW. It works OK.

Thank you,
    Michael.

> -----Original Message-----
> From: Wolfram Sang <wsa+renesas@...g-engineering.com>
> Sent: Sunday, June 28, 2020 2:53 PM
> To: linux-i2c@...r.kernel.org
> Cc: linux-renesas-soc@...r.kernel.org; Wolfram Sang <wsa+renesas@...g-
> engineering.com>; Vadim Pasternak <vadimp@...lanox.com>; Michael Shych
> <michaelsh@...lanox.com>; Wolfram Sang <wsa@...nel.org>; linux-
> kernel@...r.kernel.org
> Subject: [RFC PATCH 1/2] i2c: mlxcpld: check correct size of maximum RECV_LEN
> packet
> 
> I2C_SMBUS_BLOCK_MAX defines already the maximum number as defined in
> the
> SMBus 2.0 specs. I don't see a reason to add 1 here. Also, fix the errno
> to what is suggested for this error.
> 
> Fixes: c9bfdc7c16cb ("i2c: mlxcpld: Add support for smbus block read
> transaction")
> Signed-off-by: Wolfram Sang <wsa+renesas@...g-engineering.com>
> ---
> 
> Only build tested, I don't have the HW. Please let me know if I
> overlooked something, but to the best of my knowledge, this +1 is wrong.
> 
>  drivers/i2c/busses/i2c-mlxcpld.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-mlxcpld.c b/drivers/i2c/busses/i2c-mlxcpld.c
> index 2fd717d8dd30..71d7bae2cbca 100644
> --- a/drivers/i2c/busses/i2c-mlxcpld.c
> +++ b/drivers/i2c/busses/i2c-mlxcpld.c
> @@ -337,9 +337,9 @@ static int mlxcpld_i2c_wait_for_tc(struct mlxcpld_i2c_priv
> *priv)
>  		if (priv->smbus_block && (val &
> MLXCPLD_I2C_SMBUS_BLK_BIT)) {
>  			mlxcpld_i2c_read_comm(priv,
> MLXCPLD_LPCI2C_NUM_DAT_REG,
>  					      &datalen, 1);
> -			if (unlikely(datalen > (I2C_SMBUS_BLOCK_MAX + 1))) {
> +			if (unlikely(datalen > I2C_SMBUS_BLOCK_MAX)) {
>  				dev_err(priv->dev, "Incorrect smbus block read
> message len\n");
> -				return -E2BIG;
> +				return -EPROTO;
>  			}
>  		} else {
>  			datalen = priv->xfer.data_len;
> --
> 2.20.1