Messages in this thread | | | Subject | Re: [PATCH v2 1/1] PCI: brcmstb: Use BIT() as __GENMASK() is for internal use only | From | Florian Fainelli <> | Date | Tue, 16 Nov 2021 12:41:28 -0800 |
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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@linux.intel.com> 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@arm.com> 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 [unhandled content-type:application/pkcs7-signature] | |