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    SubjectRe: [PATCH V4 1/4] arm_pmu: acpi: Refactor arm_spe_acpi_register_device()
    On Wed, Aug 09, 2023 at 01:54:55PM +0100, Suzuki K Poulose wrote:
    > On 08/08/2023 14:16, Will Deacon wrote:
    > > On Tue, Aug 08, 2023 at 09:48:16AM +0100, Suzuki K Poulose wrote:
    > > > On 08/08/2023 09:22, Anshuman Khandual wrote:
    > > > > Sanity checking all the GICC tables for same interrupt number, and ensuring
    > > > > a homogeneous ACPI based machine, could be used for other platform devices
    > > > > as well. Hence this refactors arm_spe_acpi_register_device() into a common
    > > > > helper arm_acpi_register_pmu_device().
    > > > >
    > > > > Cc: Catalin Marinas <catalin.marinas@arm.com>
    > > > > Cc: Will Deacon <will@kernel.org>
    > > > > Cc: Mark Rutland <mark.rutland@arm.com>
    > > > > Cc: linux-arm-kernel@lists.infradead.org
    > > > > Cc: linux-kernel@vger.kernel.org
    > > > > Co-developed-by: Will Deacon <will@kernel.org>
    > > > > Signed-off-by: Will Deacon <will@kernel.org>
    > > > > Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
    > > > > ---
    > > > > drivers/perf/arm_pmu_acpi.c | 105 ++++++++++++++++++++++--------------
    > > > > 1 file changed, 65 insertions(+), 40 deletions(-)
    > > > >
    > > > > diff --git a/drivers/perf/arm_pmu_acpi.c b/drivers/perf/arm_pmu_acpi.c
    > > > > index 90815ad762eb..72454bef2a70 100644
    > > > > --- a/drivers/perf/arm_pmu_acpi.c
    > > > > +++ b/drivers/perf/arm_pmu_acpi.c
    > > > > + pdev->resource[0].start = irq;
    > > > > + ret = platform_device_register(pdev);
    > > > > + if (ret < 0) {
    > > > > + pr_warn("ACPI: %s: Unable to register device\n", pdev->name);
    > > > > + acpi_unregister_gsi(gsi);
    > > > > + }
    > > > > + return ret;
    > > >
    > > > A postivie return value here could confuse the caller. Also, with my comment
    > > > below, we don't really need to return something from here.
    > >
    > > How does this return a positive value?
    >
    > Right now, there aren't. My point is this function returns a "return value"
    > of another function. And the caller of this function doesn't
    > really follow the "check" it needs. e.g.:
    >
    > ret = foo();
    > if (ret < 0)
    > error;
    > return ret;
    >
    >
    >
    > And the caller only checks for
    >
    > if (ret)
    > error;
    >
    > This seems fragile.

    Yeah, the '< 0' check is weird. I'd be inclined to drop that entirely
    from the helper function tbh...

    > > > > + int ret = arm_acpi_register_pmu_device(&spe_dev, ACPI_MADT_GICC_SPE,
    > > > > + arm_spe_parse_gsi);
    > > > > + if (ret)
    > > > > pr_warn("ACPI: SPE: Unable to register device\n");
    > > >
    > > > With this change, a system without SPE interrupt description always
    > > > generates the above message. Is this intended ?
    > >
    > > If there are no irqs, why doesn't this return 0?
    >
    > Apologies, I missed that.
    >
    > > arm_acpi_register_pmu_device() should only fail if either:
    > >
    > > - The static resources passed in are broken
    > > - The tables are not homogeneous
    > > - We fail to register the interrupt
    > >
    > > so something is amiss.
    >
    > Agreed. We don't need duplicate messages about an error ?
    > i.e., one in arm_acpi_register_pmu_device() and another
    > one in the caller ? (Of course adding any missing error msgs).

    ... and then just print the registration failure message in the caller.

    Will

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