Messages in this thread | | | From | "Ardelean, Alexandru" <> | Subject | Re: [PATCH 3/3][V3] iio: Handle enumerated properties with gaps | Date | Fri, 5 Jul 2019 13:35:14 +0000 |
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On Thu, 2019-05-09 at 10:31 +0300, Alexandru Ardelean wrote: > On Wed, 2019-05-08 at 16:17 +0300, Andy Shevchenko wrote: > > [External] > > > > > > On Wed, May 08, 2019 at 02:19:13PM +0300, Alexandru Ardelean wrote: > > > From: Lars-Peter Clausen <lars@metafoo.de> > > > > > > Some enums might have gaps or reserved values in the middle of their > > > value > > > range. E.g. consider a 2-bit enum where the values 0, 1 and 3 have a > > > meaning, but 2 is a reserved value and can not be used. > > > > > > Add support for such enums to the IIO enum helper functions. A reserved > > > values is marked by setting its entry in the items array to NULL rather > > > than the normal descriptive string value. > > > > > > Also, `__sysfs_match_string()` now supports NULL gaps, so that doesn't > > > require any changes. > > > - for (i = 0; i < e->num_items; ++i) > > > + for (i = 0; i < e->num_items; ++i) { > > > + if (!e->items[i]) > > > + continue; > > > len += scnprintf(buf + len, PAGE_SIZE - len, "%s ", e- > > > > items[i]); > > > + } > > > > The problem here that the user will have no clue where the gap is > > happened, to > > solve this we need either bitmap of array, where set bits shows defined > > items, > > or use comma-separated list of values. The latter would need another node > > since > > we don't break user space. > > Hmmm. > I am wondering if there are cases where userspace would care about reserved > values and/or positions of reserved bit-fields. > Maybe you could offer examples/use-cases where this is needed. > > To some extent the kernel [drivers & frameworks] should probably not need > to expose that "string-enum-X" == `bitfield_2` matching; otherwise it > doesn't really add much value ; the whole point of frameworks [in general] > is to offer some level of abstraction to HW. > > The only example I can think of [atm], is when a reserved bit-field will be > used in the future. But then, the driver should care about this, and not > the framework. The driver should decide that "bitfield_2" will > enable/disable something [in the future], and should be considered in a > such a way (when being written). If the driver can't make this prediction [ > about "bitfield_2"] then a new driver must be written anyway. > > But I will agree that I may not have all arguments in mind to be 100% sure > of all this. >
Hey,
Is there any feedback/counter-arguments for this?
Thanks Alex
> Thanks > Alex > > > -- > > With Best Regards, > > Andy Shevchenko > > > >
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