linux-kernel - Re: [PATCH v2 1/2] ACPI/PPTT: Add support for ACPI 6.3 thread flag

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Message-ID: <20190625152029.GA2308@e107155-lin>
Date:   Tue, 25 Jun 2019 16:20:38 +0100
From:   Sudeep Holla <sudeep.holla@....com>
To:     Valentin Schneider <valentin.schneider@....com>
Cc:     Jeremy Linton <jeremy.linton@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org, catalin.marinas@....com,
        will.deacon@....com, rjw@...ysocki.net, lenb@...nel.org,
        Sudeep Holla <sudeep.holla@....com>
Subject: Re: [PATCH v2 1/2] ACPI/PPTT: Add support for ACPI 6.3 thread flag

On Mon, Jun 17, 2019 at 01:34:51PM +0100, Valentin Schneider wrote:
> Hi Jeremy,
>
> Few nits below.
>
> Also, I had a look at the other PPTT processor flags that were introduced
> in 6.3, and the only other one being used is ACPI_LEAF_NODE in
> acpi_pptt_leaf_node(). However that one already has a handle on the table
> header, so the check_acpi_cpu_flag() isn't of much help there.
>
> I don't believe the other existing flags will benefit from the helper since
> they are more about describing the PPTT tree, but I think it doesn't hurt
> to keep it around for potential future flags.
>
> On 14/06/2019 23:31, Jeremy Linton wrote:
> [...]
> > @@ -517,6 +517,43 @@ static int find_acpi_cpu_topology_tag(unsigned int cpu, int level, int flag)
> >  	return retval;
> >  }
> >
> > +/**
> > + * check_acpi_cpu_flag() - Determine if CPU node has a flag set
> > + * @cpu: Kernel logical CPU number
> > + * @rev: The PPTT revision defining the flag
> > + * @flag: The flag itself

How about the "the processor structure flag being examined" ?

> > + *
> > + * Check the node representing a CPU for a given flag.
> > + *
> > + * Return: -ENOENT if the PPTT doesn't exist, the CPU cannot be found or
> > + *	   the table revision isn't new enough.
> > + * Otherwise returns flag value
> > + */
>
> Nit: strictly speaking we're not returning the flag value but its mask
> applied to the flags field. I don't think anyone will care about getting
> the actual flag value, but it should be made obvious in the doc:
>

I agree with that. I am also fine if you want to change the code to
return 0 or 1 based on the flag value. It then aligns well with comment
under acpi_pptt_cpu_is_thread. Either way, we just need consistency.

--
Regards,
Sudeep