On Tue, Jun 11, 2013 at 08:55:06PM +0100, Jonathan Cameron wrote:
> On 06/10/2013 04:42 PM, Sebastian Andrzej Siewior wrote:
> > On the am335x I export ADC channels indexed by their number as specified
> > in the datasheet. The channels are shared between the TSC & ADC and be
> > used either by TSC or the ADC. So it is possible that the TSC uses
> > chanels 0 & 1 and the ADC is using channels 2 & 3. The total number of
> > channles of the ADC is 2 but the individual numbers are 2 and 3.
> > This patch changes the check for the the requesting channel by walking
> > over the list and comparing the channel number.
> >
> This doesn't work in general. The index is not the same as channel
> (or any other form of index present). Note that modified channels may
> all have channel set to 0 (accel_x, accel_y etc for instance).
>
> The index refers directly into those channels registered.
> Is it possible for channels to move at runtime between the two units?
> I would imagine not as this is very much a case of wiring.
>
> Thus we have a fairly messy bit if interdependence in the device
> tree but it should work.
>
> I don't actually have much / any real experience of device tree configurations
> and this is Guenter's code, hence I have cc'd him.
>
> Note that it is acceptable and relatively common to have missing
> values in scan_index but that isn't really relevant here.
>
> Jonathan
> > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
> > ---
> > drivers/iio/inkern.c | 13 ++++++-------
> > 1 file changed, 6 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/iio/inkern.c b/drivers/iio/inkern.c
> > index dca4eed..1a40077 100644
> > --- a/drivers/iio/inkern.c
> > +++ b/drivers/iio/inkern.c
> > @@ -107,6 +107,7 @@ static int __of_iio_channel_get(struct iio_channel *channel,
> > struct iio_dev *indio_dev;
> > int err;
> > struct of_phandle_args iiospec;
> > + int i;
> >
> > err = of_parse_phandle_with_args(np, "io-channels",
> > "#io-channel-cells",
> > @@ -123,15 +124,13 @@ static int __of_iio_channel_get(struct iio_channel *channel,
> > indio_dev = dev_to_iio_dev(idev);
> > channel->indio_dev = indio_dev;
> > index = iiospec.args_count ? iiospec.args[0] : 0;
> > - if (index >= indio_dev->num_channels) {
> > - err = -EINVAL;
> > - goto err_put;
> > + for (i = 0; i < indio_dev->num_channels; i++) {
> > + if (indio_dev->channels[i].channel == index) {
> > + channel->channel = &indio_dev->channels[i];
> > + return 0;
> > + }
> > }
Too long ago since I looked into that, but this code changes the API
from "get nth channel" to "channel with channel index n".
Not really sure I understand why that should be necessary.
Guenter
> > - channel->channel = &indio_dev->channels[index];
> > -
> > - return 0;
> >
> > -err_put:
> > iio_device_put(indio_dev);
>
> If not found (i.e. the device tree entries are garbage) we may return sucess witout
> actually having retrieved the driver. I would suggest setting err = -EINVAL before
> the for loop.
>
> > return err;
> > }
> >
>
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