Lars-Peter Clausen <lars@xxxxxxxxxx> wrote:
>On 10/19/2011 11:04 PM, Dan Carpenter wrote:
>> On Wed, Oct 19, 2011 at 05:47:50PM +0200, Lars-Peter Clausen wrote:
>>> @@ -225,6 +226,7 @@ static int ad5791_read_raw(struct iio_dev
>*indio_dev,
>>> long m)
>>> {
>>> struct ad5791_state *st = iio_priv(indio_dev);
>>> + u64 val64;
>>> int ret;
>>>
>>> switch (m) {
>>> @@ -234,12 +236,16 @@ static int ad5791_read_raw(struct iio_dev
>*indio_dev,
>>> return ret;
>>> *val &= AD5791_DAC_MASK;
>>> *val >>= chan->scan_type.shift;
>>> - *val -= (1 << (chan->scan_type.realbits - 1));
>>> return IIO_VAL_INT;
>>> case (1 << IIO_CHAN_INFO_SCALE_SHARED):
>>> *val = 0;
>>> *val2 = (st->vref_mv * 1000) >> chan->scan_type.realbits;
>>> return IIO_VAL_INT_PLUS_MICRO;
>>> + case (1 << IIO_CHAN_INFO_OFFSET_SHARED):
>>> + val64 = (((u64)st->vref_neg_mv) << chan->scan_type.realbits);
>>> + do_div(val64, st->vref_mv);
>>> + *val = -val64;
>>> + return IIO_VAL_INT;
>>
>> Why does iio use switch over a bitfield? If the values are mutually
>> exclusive then why not just use an enum?
>>
>
>I wondered the very same and couldn't find a good explanation. I wanted
>to
>write a small RFC today converting the core and maybe 2-3 drivers to
>use the
>unshifted variants to see what Jonathan thinks about it.
It is legacy cruft from a while back. So I would be happy to see it go.
>
>> Hm... "m" stands for mask and it gets created using the
>> IIO_UNMOD_EVENT_CODE() macro or sometimes it's just one bit at a
>> time copied from &chan->info_mask... Odd.
>>
>
>IIO_UNMOD_EVENT_CODE is only used for events which use a different
>callback
>function, so for the read_raw/write_raw callbacks we currently only
>ever
>pass one channel info type at a time.
>
>- Lars
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