On Thu, 5 Oct 2023 19:50:18 -0500 David Lechner <dlechner@xxxxxxxxxxxx> wrote: > When reading registers on the AD2S1210 chip, we have to supply a "dummy" > address for the second SPI tx byte so that we don't accidentally write > to a register. This register will be read and the value discarded on the > next regmap read or write call. > > Reading the fault register has a side-effect of clearing the faults > so we should not use this register for the dummy read. > > Signed-off-by: David Lechner <dlechner@xxxxxxxxxxxx> ouch. Applied to the togreg branch of iio.git and pushed out as testing for 0day to take a look at it. Thanks, Jonathan > --- > > v4 changes: New patch > > (this probably should have been done before "staging: iio: resolver: > ad2s1210: use regmap for config registers" but was overlooked until now) > > drivers/staging/iio/resolver/ad2s1210.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/drivers/staging/iio/resolver/ad2s1210.c b/drivers/staging/iio/resolver/ad2s1210.c > index 67d8af0dd7ae..8fbde9517fe9 100644 > --- a/drivers/staging/iio/resolver/ad2s1210.c > +++ b/drivers/staging/iio/resolver/ad2s1210.c > @@ -166,9 +166,10 @@ static int ad2s1210_regmap_reg_read(void *context, unsigned int reg, > st->tx[0] = reg; > /* > * Must be valid register address here otherwise this could write data. > - * It doesn't matter which one. > + * It doesn't matter which one as long as reading doesn't have side- > + * effects. > */ > - st->tx[1] = AD2S1210_REG_FAULT; > + st->tx[1] = AD2S1210_REG_CONTROL; > > ret = spi_sync_transfer(st->sdev, xfers, ARRAY_SIZE(xfers)); > if (ret < 0) >
