Messages in this thread | | | Date | Thu, 13 Apr 2023 08:48:08 +0300 | From | Matti Vaittinen <> | Subject | Re: [PATCH 1/3] iio: core: add IIO_VAL_INT_MICRO |
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Hi Jonathan,
On 4/12/23 23:32, Jonathan Cameron wrote: > On Wed, 12 Apr 2023 15:27:14 +0300 > Matti Vaittinen <mazziesaccount@gmail.com> wrote: > >> There are a few cases like light sensor integration times, where values >> returned from *_available() and read_raw() are smaller than 1 and often >> in the units of micro. (Like micro second scale integration times, >> always smaller than 1 second). Currently those are often handled using >> IIO_VAL_INT_PLUS_MICRO, which requires drivers to initialize the integer >> part to zero. Furthermore, using IIO_VAL_INT_PLUS_MICRO in iio lists >> requires one to always allocate the 'dummy' integer part too. >> >> Introduce IIO_VAL_INT_MICRO which allows omitting the always zero integer. >> >> Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com> > Hi Matti, > > I'm not keen on adding yet another case just to avoid having to > have the integer part for IIO_VAL_INT_PLUS_MICRO. > Seems like the wrong trade off of maintainability vs ease of use.
I see your point. I would still argue that adding the IIO_VAL_INT_MICRO was not really an intrusive change and I'd expect the maintenance effort should not be increased that much.
While the inconvenience for users in read_raw (initializing the *val = 0) is minor (meaning the benefit of adding IIO_VAL_INT_MICRO is also minor in this regard), iio_lists are stronger reason to consider this. With IIO_VAL_INT_MICRO the iio-list memory footprint will be halved. In my opinion, this benefit would exceed the cost of maintenance effort increase - sure thing it's easy for me to say as I am not the maintainer ;) (And as I wrote, this series was cooked in a hurry - I had no time to go through existing drivers to see how many could benefit from the new IIO_VAL_INT_MICRO. I may do this later when I get some pretty urgent things off my shoulders - assuming you're not opposing this change so strongly that this is out of the question no matter how many existing users could benefit from IIO_VAL_INT_MICRO).
Anyways, if this is your final stance, then I need to rework the integration time list allocations in the gts helper, but I am most likely not able to do this until a week or two from now - meaning it might be better to revert the bu27034 and iio-gts-helpers until this gets fixed. (I reserve the right to do this during some night if I can't get sleep though.)
Yours, -- Matti
> Jonathan > >> --- >> drivers/iio/industrialio-core.c | 4 ++++ >> include/linux/iio/types.h | 1 + >> 2 files changed, 5 insertions(+) >> >> diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c >> index c117f50d0cf3..c5ae965e9961 100644 >> --- a/drivers/iio/industrialio-core.c >> +++ b/drivers/iio/industrialio-core.c >> @@ -628,6 +628,8 @@ static ssize_t __iio_format_value(char *buf, size_t offset, unsigned int type, >> switch (type) { >> case IIO_VAL_INT: >> return sysfs_emit_at(buf, offset, "%d", vals[0]); >> + case IIO_VAL_INT_MICRO: >> + return sysfs_emit_at(buf, offset, "0.%06u", vals[0]); >> case IIO_VAL_INT_PLUS_MICRO_DB: >> scale_db = true; >> fallthrough; >> @@ -758,6 +760,7 @@ static ssize_t iio_format_list(char *buf, const int *vals, int type, int length, >> >> switch (type) { >> case IIO_VAL_INT: >> + case IIO_VAL_INT_MICRO: >> stride = 1; >> break; >> default: >> @@ -952,6 +955,7 @@ static ssize_t iio_write_channel_info(struct device *dev, >> case IIO_VAL_INT_PLUS_MICRO_DB: >> scale_db = true; >> fallthrough; >> + case IIO_VAL_INT_MICRO: >> case IIO_VAL_INT_PLUS_MICRO: >> fract_mult = 100000; >> break; >> diff --git a/include/linux/iio/types.h b/include/linux/iio/types.h >> index 82faa98c719a..b4e316172c7f 100644 >> --- a/include/linux/iio/types.h >> +++ b/include/linux/iio/types.h >> @@ -30,6 +30,7 @@ enum iio_event_info { >> #define IIO_VAL_FRACTIONAL 10 >> #define IIO_VAL_FRACTIONAL_LOG2 11 >> #define IIO_VAL_CHAR 12 >> +#define IIO_VAL_INT_MICRO 13 /* val is micro <units>. Integer part is 0 */ >> >> enum iio_available_type { >> IIO_AVAIL_LIST, >
-- Matti Vaittinen Linux kernel developer at ROHM Semiconductors Oulu Finland
~~ When things go utterly wrong vim users can always type :help! ~~
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