Re: [lm-sensors] [PATCH RESEND] hwmon: lm70: TI TMP121 support.

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

Hi David,

Thanks for your comments.

On Thu, 23 Oct 2008 09:53:00 -0700, David Brownell wrote:
> On Thursday 23 October 2008, Manuel Lauss wrote:
> >  	/*
> > +	 * LM70:
> >  	 * The "raw" temperature read into rxbuf[] is a 16-bit signed 2's
> >  	 * complement value. Only the MSB 11 bits (1 sign + 10 temperature
> >  	 * bits) are meaningful; the LSB 5 bits are to be discarded.
> > @@ -80,8 +82,23 @@ static ssize_t lm70_sense_temp(struct device *dev,
> >  	 * by 0.25. Also multiply by 1000 to represent in millidegrees
> >  	 * Celsius.
> >  	 * So it's equivalent to multiplying by 0.25 * 1000 = 250.
> > +	 *
> > +	 * TMP121:
> > +	 * 13 bits of 2's complement data, discard LSB 3 bits.  Chip
> > +	 * transmits high byte first.  Resolution 0.0625 degrees celsius.
> 
> For SPI, everything is MSB first ... else insist (spi->mode & SPI_LSB_FIRST)
> is true.  Please strike the comment implying it might not be MSB first.

Except that the LM70 transmits the LSB first, so it seems valuable to
underline that the TMP121 behaves differently.

> >  	 */
> > -	val = ((int)raw/32) * 250;
> > +	switch (p_lm70->chip) {
> > +	case LM70_CHIP_LM70:
> > +		raw = (rxbuf[1] << 8) + rxbuf[0];
> > +		val = ((int)raw/32) * 250;
> > +		break;
> > +
> > +	case LM70_CHIP_TMP121:
> > +		raw = (rxbuf[0] << 8) + rxbuf[1];
> > +		val = (raw / 8) * 625 / 10;
> > +		break;
> > +	}
> > +	dev_dbg(dev, "raw=0x%x\n", raw);
> >  	status = sprintf(buf, "%d\n", val); /* millidegrees Celsius */
> >  out:
> >  	mutex_unlock(&p_lm70->lock);

-- 
Jean Delvare

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