On 11/16/21 10:20 AM, Rob Herring wrote: > +Marc Z > > On Mon, Nov 15, 2021 at 8:39 AM Andy Shevchenko > <andriy.shevchenko@xxxxxxxxxxxxxxx> wrote: >> >> On Mon, Nov 15, 2021 at 04:14:21PM +0200, Andy Shevchenko wrote: >>> On Mon, Nov 15, 2021 at 4:01 PM Robin Murphy <robin.murphy@xxxxxxx> wrote: >>>> On 2021-11-15 11:20, Andy Shevchenko wrote: >>>>> Use BIT() as __GENMASK() is for internal use only. The rationale >>>>> of switching to BIT() is to provide better generated code. The >>>>> GENMASK() against non-constant numbers may produce an ugly assembler >>>>> code. On contrary the BIT() is simply converted to corresponding shift >>>>> operation. >>>> >>>> FWIW, If you care about code quality and want the compiler to do the >>>> obvious thing, why not specify it as the obvious thing: >>>> >>>> u32 val = ~0 << msi->legacy_shift; >>> >>> Obvious and buggy (from the C standard point of view)? :-) >> >> Forgot to mention that BIT() is also makes it easy to avoid such mistake. >> >>>> Personally I don't think that abusing BIT() in the context of setting >>>> multiple bits is any better than abusing __GENMASK()... >>> >>> No, BIT() is not abused here, but __GENMASK(). >>> >>> After all it's up to you, folks, consider that as a bug report. > > Couldn't we get rid of legacy_shift entirely if the legacy case sets > up 'hwirq' as 24-31 rather than 0-7? Though the data for the MSI msg > uses the hwirq. I personally find it clearer and easier to reason about with the current code though I suppose that with an appropriate xlate method we could sort of set up the hwirq the way we want them to be to avoid any shifting in brcm_pcie_msi_isr(). -- Florian
Attachment:
smime.p7s
Description: S/MIME Cryptographic Signature
