Re: [PATCH 5/6] iio:common:ms_sensors:ms_sensors_i2c: add support for alternative PROM layout

Alexandre Belloni
2020-12-13T19:36:03Z

On 13/12/2020 17:20:42+0000, Jonathan Cameron wrote:
> > +/**
> > + * ms_sensors_tp_crc_valid_112() - CRC check function for
> > + * Temperature and pressure devices for 112bit PROM.
> > + * This function is only used when reading PROM coefficients
> > + *
> > + * @prom: pointer to PROM coefficients array
> > + *
> > + * Return: CRC.
>
> That's a bit confusing. Perhaps return if CRC correct
> Sometimes CRC is used to refer to particular bits and sometimes
> to the check (i.e. whether it is right).
>

Roght, this should have been "Return: True if CRC is ok."

> > + */
> > +static bool ms_sensors_tp_crc_valid_112(u16 *prom)
> > +{
> > + u16 w0 = prom[0], crc_read = (w0 & 0xF000) >> 12;
> > + u8 crc;
> > +
> > + prom[0] &= 0x0FFF; /* Clear the CRC computation part */
> > + prom[MS_SENSORS_TP_PROM_WORDS_NB - 1] = 0;
> > +
> > + crc = ms_sensors_tp_crc4(prom);
> > +
> > + prom[0] = w0;
> > +
> > + return crc == crc_read;
> > +}
> > +
> > +/**
> > + * ms_sensors_tp_crc_valid_128() - CRC check function for
> > + * Temperature and pressure devices for 128bit PROM.
> > + * This function is only used when reading PROM coefficients
> > + *
> > + * @prom: pointer to PROM coefficients array
> > + *
> > + * Return: CRC.
> > + */
> > +static bool ms_sensors_tp_crc_valid_128(u16 *prom)
> > +{
> > + u16 w7 = prom[7], crc_read = w7 & 0x000F;
> > + u8 crc;
> > +
> > + prom[7] &= 0xFF00; /* Clear the CRC and LSB part */
> > +
> > + crc = ms_sensors_tp_crc4(prom);
> > +
> > + prom[7] = w7;
> > +
> > + return crc == crc_read;
> > }
> >
> > /**
> > @@ -535,6 +577,7 @@ static bool ms_sensors_tp_crc_valid(u16 *prom)
> > int ms_sensors_tp_read_prom(struct ms_tp_dev *dev_data)
> > {
> > int i, ret;
> > + bool valid;
> >
> > for (i = 0; i < dev_data->hw->prom_len; i++) {
> > ret = ms_sensors_read_prom_word(
> > @@ -546,7 +589,12 @@ int ms_sensors_tp_read_prom(struct ms_tp_dev *dev_data)
> > return ret;
> > }
> >
> > - if (!ms_sensors_tp_crc_valid(dev_data->prom)) {
> > + if (dev_data->hw->prom_len == 8)
> > + valid = ms_sensors_tp_crc_valid_128(dev_data->prom);
> > + else
> > + valid = ms_sensors_tp_crc_valid_112(dev_data->prom);
> > +
> > + if (!valid) {
> > dev_err(&dev_data->client->dev,
> > "Calibration coefficients crc check error\n");
> > return -ENODEV;
>

--
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering