On Mon, 2019-04-22 at 23:06 +0200, Greg KH wrote: > > > On Mon, Apr 22, 2019 at 11:32:56AM +0300, Alexandru Ardelean wrote: > > This helper is similar to __sysfs_match_string() with the exception > > that it > > ignores NULL elements within the array. > > sysfs is "one value per file", why are you trying to write multiple > things on a single line to a single sysfs file? > > Is IIO really that messy? :) > Hmm, I don't think I understood the comment/question, or maybe I did not formulate the comment properly. Maybe Jonathan can pitch-in here if I'm saying something wrong. So, in IIO there is `struct iio_enum` which is essentially a sysfs wrapper for exposing an "enum" type to userspace via sysfs (which takes only one value). This iio_enum type is basically a string-to-int mapping. Some example in C: enum { ENUM0, ENUM1, ENUM5 = 5, ENUM6, ENUM7 }; /* Notice the gaps in the elements */ static const char * const item_strings[] = { [ENUM0] = "mode0", [ENUM1] = "mode1", [ENUM5] = "mode5", [ENUM6] = "mode6", [ENUM7] = "mode7", }; static const struct iio_enum iio_enum1 = { .items = item_strings, .num_items = ARRAY_SIZE(item_strings), .set = iio_enum1_set, .get = iio_enum1_get, }; The signature of the iio_enum1_set / iio_enum1_get is below: static int iio_enum1_set(struct iio_dev *indio_dev, const struct iio_chan_spec *chan, unsigned int val); static int iio_enum1_get(struct iio_dev *indio_dev, const struct iio_chan_spec *chan) IIO core resolves the string-to-int mapping. It uses __sysfs_match_string() to do that, but it requires that the list of strings (and C enums) be contiguous. This change [and V2 of this patch] introduces a __sysfs_match_string_with_gaps() helper that ignores gaps (represented as NULLs). For reference, __sysfs_match_string() returns -EINVAL on the first NULL in the array of strings (regardless of the given array size). __sysfs_match_string_with_gaps() is typically helpful when C enums refer to bitfields, or have some equivalence in HW. Thanks Alex > thanks, > > greg k-h