Hi Jonathan,
On 4/12/23 23:32, Jonathan Cameron wrote:
On Wed, 12 Apr 2023 15:27:14 +0300
Matti Vaittinen <mazziesaccount@xxxxxxxxx> 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@xxxxxxxxx>
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! ~~
