linux-kernel - Re: [PATCH v3 1/2] acpi/x86: Fix improper handling of SCI INT for platforms supporting only IOAPIC mode

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Date:   Fri, 17 Nov 2017 11:38:05 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Vikas C Sajjan <vikas.cha.sajjan@....com>
cc:     rjw@...ysocki.net, linux-pm@...r.kernel.org,
        linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
        kkamagui@...il.com, mingo@...nel.org
Subject: Re: [PATCH v3 1/2] acpi/x86: Fix improper handling of SCI INT for
 platforms supporting only IOAPIC mode

On Thu, 16 Nov 2017, Vikas C Sajjan wrote:

> The platforms which support only IOAPIC mode, pass the SCI information
> above the legacy space (0-15) via the FADT mechanism and not via MADT.
> In such cases the mp_override_legacy_irq() used by acpi_sci_ioapic_setup()
> to register SCI interrupts fails for interrupts >= 16, since it is meant to
> handle only legacy space and throws error "Invalid bus_irq %u for legacy
> override". Hence add a new function to handle SCI interrupts >= 16 and
> invoke it conditionally in acpi_sci_ioapic_setup().The code duplication
> due to this new function will be cleaned up in a separate patch.

This reads way better, but I have a small nit pick. In the example I gave
you there were multiple paragraphs on purpose to separate the different
parts. So if I just split the above lump into separate paragraphs:

[1]
   The platforms which support only IOAPIC mode, pass the SCI information
   above the legacy space (0-15) via the FADT mechanism and not via MADT.

[2]
   In such cases the mp_override_legacy_irq() used by acpi_sci_ioapic_setup()
   to register SCI interrupts fails for interrupts >= 16, since it is meant to
   handle only legacy space and throws error "Invalid bus_irq %u for legacy
   override".

[3]
   Hence add a new function to handle SCI interrupts >= 16 and
   invoke it conditionally in acpi_sci_ioapic_setup().

[4]
   The code duplication due to this new function will be cleaned up in a
   separate patch.

then this is clearly structured:

[1] describes the context.

[2] describes the failure

[3] describes the solution

[4] is an extra note to tell the reviewer/reader that you are aware of the
    code duplication and this is addressed later. 

No need to resend. I can do that when picking it up.

> Co-developed-by: Sunil V L <sunil.vl@....com>

I had a discussion with Greg about this tag which resulted in a patch so
it should be soon part of the official documentation:

 https://lkml.kernel.org/r/20171116132309.GA8449@kroah.com

We agreed that both authors should add their Signed-off-by to document that
the work conforms with the Developer Certificate of Origin. I'll add that
if that's ok for you.

Thanks for following up!

       tglx