Messages in this thread | | | Date | Mon, 28 Mar 2022 17:49:44 +0100 | From | Jonathan Cameron <> | Subject | Re: [PATCH] iio:proximity:sx9324: Fix hardware gain read/write |
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On Mon, 28 Mar 2022 01:16:10 +0300 Andy Shevchenko <andy.shevchenko@gmail.com> wrote:
> On Sat, Mar 19, 2022 at 5:58 AM Stephen Boyd <swboyd@chromium.org> wrote: > > > > There are four possible gain values according to sx9324_gain_vals[]: 1, > > 2, 4, and 8. When writing and reading the register the values are off by > > one. The bits should be set according to this equation: > > > > ilog2(<gain>) + 1 > > > > so that a gain of 8 is 0x3 in the register field and a gain of 4 is 0x2 > > in the register field, etc. Fix up the functions. > > ... > > > + *val = 1 << regval; > > I see it's similar in the original code, but this is still problematic > from C standard point of view, i.e. if regval = 31, the C standard > calls it UB (Undefined Behaviour). >
I don't see that as a problem as regval is coming from a FIELD_GET() with a 3 bit mask so we can't hit the UB case (can only be up to 7 - well 6 because of the --)
Jonathan
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