linux-kernel - Re: [PATCH v7 03/15] i2c: octeon: Remove I2C_FUNC_SMBUS

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Date:	Tue, 26 Apr 2016 00:16:22 +0200
From:	Wolfram Sang <wsa@...-dreams.de>
To:	Jan Glauber <jglauber@...ium.com>
Cc:	linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org,
	David Daney <ddaney@...iumnetworks.com>
Subject: Re: [PATCH v7 03/15] i2c: octeon: Remove I2C_FUNC_SMBUS_QUICK support

On Mon, Apr 25, 2016 at 04:33:32PM +0200, Jan Glauber wrote:
> SMBUS QUICK never worked for the read case, because EINVAL was returned
> for a zero length message. The hardware does not support SMBUS QUICK
> messages so disable the support and remove the zero length check.
> 
> Signed-off-by: Jan Glauber <jglauber@...ium.com>

I see better now and I think we need to drop this patch. It looks like
the driver supports only SMBUS_QUICK_WRITE which can be used for
scanning devices. The driver probably works with 'i2cdetect -q'. This
will regress if I apply the patch.

It seems it can't do SMBUS_QUICK_READ thus the extra check in the code.

I2C_FUNC_SMBUS_QUICK should have been split up in READ and WRITE to
support this scenario.

Are my assumptions correct?


> ---
>  drivers/i2c/busses/i2c-octeon.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-octeon.c b/drivers/i2c/busses/i2c-octeon.c
> index 0f536a1..ad563cf 100644
> --- a/drivers/i2c/busses/i2c-octeon.c
> +++ b/drivers/i2c/busses/i2c-octeon.c
> @@ -459,9 +459,6 @@ static int octeon_i2c_read(struct octeon_i2c *i2c, int target,
>  	int i, result, length = *rlength;
>  	bool final_read = false;
>  
> -	if (length < 1)
> -		return -EINVAL;
> -
>  	octeon_i2c_data_write(i2c, (target << 1) | 1);
>  	octeon_i2c_ctl_write(i2c, TWSI_CTL_ENAB);
>  
> @@ -597,7 +594,7 @@ static struct i2c_bus_recovery_info octeon_i2c_recovery_info = {
>  
>  static u32 octeon_i2c_functionality(struct i2c_adapter *adap)
>  {
> -	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL |
> +	return I2C_FUNC_I2C | (I2C_FUNC_SMBUS_EMUL & ~I2C_FUNC_SMBUS_QUICK) |
>  	       I2C_FUNC_SMBUS_READ_BLOCK_DATA | I2C_SMBUS_BLOCK_PROC_CALL;
>  }
>  
> -- 
> 1.9.1
> 

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