Re: [PATCH] i2c/mips: Fix error return codes from Sibyte i2c bus driver

[Jean Delvare <khali@linux-fr.org>]

On Sat, 26 Jun 2010 17:14:59 +0100 (BST), Maciej W. Rozycki wrote:
> On Tue, 22 Jun 2010, Guenter Roeck wrote:
> 
> > > > @@ -104,7 +104,7 @@ static int smbus_xfer(struct i2c_adapter *i2c_adap, u16 addr,
> > > >  	if (error & M_SMB_ERROR) {
> > > >  		/* Clear error bit by writing a 1 */
> > > >  		csr_out32(M_SMB_ERROR, SMB_CSR(adap, R_SMB_STATUS));
> > > > -		return -1;      /* XXXKW better error code? */
> > > > +		return -ENXIO;
> > > >  	}
> > > >  
> > > >  	if (data_bytes == 1)
> > > 
> > > Definitely an improvement. However, returning -ENXIO on all errors
> > > seems wrong. This error value should only be returned on missing ack
> > > from the slave on address byte. Isn't it possible to distinguish
> > > between different error kinds? M_SMB_ERROR_TYPE seems promising, but
> > > one would need to look up the datasheet (which I don't have) to
> > > discover its meaning.
> > > 
> > Makes sense. I'll dig up a copy of the datasheet and see if I can improve it.
> 
>  The M_SMB_ERROR_TYPE bit is cleared if an expected ackonwledgement has 
> not been seen and set if the transfer has failed after 15 retries.  So 
> that's probably ENXIO for the former and EIO for the latter.

Exactly what Guenter did. Good.

-- 
Jean Delvare