Messages in this thread | | | From | "Ardelean, Alexandru" <> | Subject | Re: [PATCH 1/2] lib: add __sysfs_match_string_with_gaps() helper | Date | Tue, 23 Apr 2019 06:38:44 +0000 |
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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
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