On Sun, 19 May 2024 22:32:50 +0200 Dimitri Fedrau <dima.fedrau@xxxxxxxxx> wrote: > Am Sun, May 19, 2024 at 05:14:38PM +0100 schrieb Jonathan Cameron: > > On Fri, 17 May 2024 10:10:49 +0200 > > Dimitri Fedrau <dima.fedrau@xxxxxxxxx> wrote: > > > > > The mapping from cold junction to ambient temperature is inaccurate. We > > > provide an index for hot and cold junction temperatures. > > > > > > Suggested-by: Jonathan Cameron <jic23@xxxxxxxxxx> > > > Signed-off-by: Dimitri Fedrau <dima.fedrau@xxxxxxxxx> > > Hi Dmitri, > > > Hi Jonathan, > > > I'm not sure you replied to the question in previous review of what > > sysfs files exist for this device. Whilst I am at least a little > > open to changing the ABI, I'd like to fully understand what > > is currently presented and why iio_info is having trouble with it. > > > I did, see: https://lore.kernel.org/linux-iio/20240509193125.GA3614@debian/T/#u Ah thanks! Oddly seem to have missed that on my other email account, but have it here. Thanks for the link. > > But maybe not to the point. Sysfs is working correct and iio_info > probably not. There is only one channel found, the temp_ambient. I would > have expected two channels. Instead there are four attributes, I would > have expected two. It seems to me that they are just duplicated. I also > added the output when setting channel2 member of channel 0 to > IIO_MOD_TEMP_OBJECT. This time iio_info works fine. I'd be tempted to look at whether iio_info can be easily 'fixed' as a starting point. This corner case may well occur for other devices in future. It is 'stretching' the ABI definition but I don't think the current documentation rules this case out. > > > I also want an ack from Andrew on this one given might break it existing > > usage. > > > > The current interface is perhaps less than ideal, but I don't think it > > is wrong as such. Whilst I wasn't particularly keen on the cold junction > > == ambient I'm not sure moving to just indexed is an improvement. > > Hence looking for input from Andrew. +CC Nuno as someone who is both > > active in IIO and has written thermocouple front end drivers in > > the past. > > > I just thought the setting of channel2 member to IIO_MOD_TEMP_OBJECT was > missing. But it turned out that it is not set for a reason. I'm fine > with the existing mapping, but would be still interesting to know how > others think about the mapping. Agreed - I'm not sure on the right thing to do here. I suspect leaving the modifier and add the index may be the best we can do but let us wait to see what others think. Jonathan > > Dimitri > > > > > > --- > > > drivers/iio/temperature/mcp9600.c | 9 +++++++-- > > > 1 file changed, 7 insertions(+), 2 deletions(-) > > > > > > diff --git a/drivers/iio/temperature/mcp9600.c b/drivers/iio/temperature/mcp9600.c > > > index 46845804292b..22451d1d9e1f 100644 > > > --- a/drivers/iio/temperature/mcp9600.c > > > +++ b/drivers/iio/temperature/mcp9600.c > > > @@ -14,6 +14,9 @@ > > > > > > #include <linux/iio/iio.h> > > > > > > +#define MCP9600_CHAN_HOT_JUNCTION 0 > > > +#define MCP9600_CHAN_COLD_JUNCTION 1 > > > + > > > /* MCP9600 registers */ > > > #define MCP9600_HOT_JUNCTION 0x0 > > > #define MCP9600_COLD_JUNCTION 0x2 > > > @@ -25,17 +28,19 @@ > > > static const struct iio_chan_spec mcp9600_channels[] = { > > > { > > > .type = IIO_TEMP, > > > + .channel = MCP9600_CHAN_HOT_JUNCTION, > > > .address = MCP9600_HOT_JUNCTION, > > > .info_mask_separate = > > > BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE), > > > + .indexed = 1, > > > }, > > > { > > > .type = IIO_TEMP, > > > + .channel = MCP9600_CHAN_COLD_JUNCTION, > > > .address = MCP9600_COLD_JUNCTION, > > > - .channel2 = IIO_MOD_TEMP_AMBIENT, > > > - .modified = 1, > > > .info_mask_separate = > > > BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE), > > > + .indexed = 1, > > > }, > > > }; > > > > > >
