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Subject: Re: [PATCH] i2c-powermac: Reject unsupported I2C transactions
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Jean Delvare <khali@linux-fr.org>
In-Reply-To: <20090930221435.58636363@hyperion.delvare>
References: <20090930221435.58636363@hyperion.delvare>
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Date: Wed, 14 Oct 2009 16:39:48 +1100
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Cc: linuxppc-dev@ozlabs.org, Paul Mackerras <paulus@samba.org>,
	Linux I2C <linux-i2c@vger.kernel.org>
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On Wed, 2009-09-30 at 22:14 +0200, Jean Delvare wrote:
> The i2c-powermac driver doesn't support arbitrary multi-message I2C
> transactions, only SMBus ones. Make it clear by returning an error if
> a multi-message I2C transaction is attempted. This is better than only
> processing the first message, because most callers won't recover from
> the short transaction. Anyone wishing to issue multi-message
> transactions should use the SMBus API instead of the raw I2C API.
> 
> Signed-off-by: Jean Delvare <khali@linux-fr.org>

Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

> Cc: Paul Mackerras <paulus@samba.org>
> ---
>  drivers/i2c/busses/i2c-powermac.c |    6 ++++++
>  1 file changed, 6 insertions(+)
> 
> --- linux-2.6.32-rc1.orig/drivers/i2c/busses/i2c-powermac.c	2009-06-10 05:05:27.000000000 +0200
> +++ linux-2.6.32-rc1/drivers/i2c/busses/i2c-powermac.c	2009-09-30 20:29:42.000000000 +0200
> @@ -146,6 +146,12 @@ static int i2c_powermac_master_xfer(	str
>  	int			read;
>  	int			addrdir;
>  
> +	if (num != 1) {
> +		dev_err(&adap->dev,
> +			"Multi-message I2C transactions not supported\n");
> +		return -EOPNOTSUPP;
> +	}
> +
>  	if (msgs->flags & I2C_M_TEN)
>  		return -EINVAL;
>  	read = (msgs->flags & I2C_M_RD) != 0;
> 
>