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;
> + }
> }
> - 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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