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From: Ingo Molnar <mingo@kernel.org>
To: Julia Lawall <julia.lawall@lip6.fr>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
	x86@kernel.org, Andi Kleen <andi@firstfloor.org>,
	linux-kernel@vger.kernel.org, Darren Hart <dvhart@infradead.org>,
	platform-driver-x86@vger.kernel.org,
	Bhumika Goyal <bhumirks@gmail.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH v1] x86/platform/intel-mid: Revert "Make 'bt_sfi_data' const"
Date: Thu, 28 Dec 2017 13:53:41 +0100	[thread overview]
Message-ID: <20171228125341.46xng2mzagksfyhr@gmail.com> (raw)
In-Reply-To: <alpine.DEB.2.20.1712281333390.2220@hadrien>


* Julia Lawall <julia.lawall@lip6.fr> wrote:

> > > [...] There does seem to be a few cases where the field actually does hold an
> > > integer.  I guess this is not a problem?
> >
> > Could you point to such an example?
> 
> drivers/thermal/intel_soc_dts_thermal.c:#define BYT_SOC_DTS_APIC_IRQ	86
> 
> and then:
> 
> static const struct x86_cpu_id soc_thermal_ids[] = {
>         { X86_VENDOR_INTEL, 6, INTEL_FAM6_ATOM_SILVERMONT1, 0,
>                 BYT_SOC_DTS_APIC_IRQ},
>         {}
> };
> 
> and finally:
> 
>  soc_dts_thres_irq = (int)match_cpu->driver_data;
> 
> Also:
> 
> arch/x86/kernel/apic/apic.c
> 
> #define DEADLINE_MODEL_MATCH_REV(model, rev)    \
> 	{ X86_VENDOR_INTEL, 6, model, X86_FEATURE_ANY, (unsigned long)rev
> }
> 
> DEADLINE_MODEL_MATCH_REV ( INTEL_FAM6_BROADWELL_X,      0x0b000020),
> DEADLINE_MODEL_MATCH_REV ( INTEL_FAM6_HASWELL_CORE,     0x22),
> etc. (all 2-digit numbers in the remaining case).

Ok - I think in these cases the resulting long->pointer type conversion is a _lot_ 
less dangerous than the pointer->long conversion which caused the regression.

So unless the resulting code is excessively ugly, this feels like the right 
approach to me.

Thanks,

	Ingo

  reply	other threads:[~2017-12-28 12:53 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-12-28 10:08 [PATCH v1] x86/platform/intel-mid: Revert "Make 'bt_sfi_data' const" Andy Shevchenko
2017-12-28 10:28 ` Ingo Molnar
2017-12-28 10:34   ` Julia Lawall
2017-12-28 11:12     ` Ingo Molnar
2017-12-28 11:23       ` Julia Lawall
2017-12-28 11:59         ` Ingo Molnar
2017-12-28 12:12   ` Andy Shevchenko
2017-12-28 12:17     ` Ingo Molnar
2017-12-28 12:25       ` Julia Lawall
2017-12-28 12:29         ` Ingo Molnar
2017-12-28 12:37           ` Julia Lawall
2017-12-28 12:53             ` Ingo Molnar [this message]
2017-12-28 14:00               ` Julia Lawall
2017-12-28 15:24                 ` Ingo Molnar
2017-12-28 15:28                   ` Julia Lawall
2017-12-28 21:22                   ` Julia Lawall
2018-01-01 15:15                   ` Julia Lawall

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