On 06/11/2013 10:44 PM, Guenter Roeck wrote:
> 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.
>
yea, this will definitively not work channels of different types will
usually have the same channel numbers.
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