linux-kernel - Re: [PATCH v6] arm64: cpuinfo: Expose MIDR_EL1 and REVIDR

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Message-ID: <20160628162755.GR31744@leverpostej>
Date:	Tue, 28 Jun 2016 17:27:56 +0100
From:	Mark Rutland <mark.rutland@....com>
To:	Catalin Marinas <catalin.marinas@....com>
Cc:	Suzuki K Poulose <suzuki.poulose@....com>, will.deacon@....com,
	steve.capper@...aro.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v6] arm64: cpuinfo: Expose MIDR_EL1 and REVIDR_EL1 to
 sysfs

On Tue, Jun 28, 2016 at 04:33:46PM +0100, Catalin Marinas wrote:
> On Tue, Jun 21, 2016 at 12:12:36PM +0100, Suzuki K. Poulose wrote:
> > +#define CPUINFO_ATTR_RO(_name)							\
> > +	static ssize_t show_##_name(struct device *dev,				\
> > +			struct device_attribute *attr, char *buf)		\
> > +	{									\
> > +		struct cpuinfo_arm64 *info = &per_cpu(cpu_data, dev->id);	\
> > +										\
> > +		if (info->reg_midr)						\
> > +			return sprintf(buf, "0x%016x\n", info->reg_##_name);	\
> > +		else								\
> > +			return 0;						\
> > +	}									\
> > +	static DEVICE_ATTR(_name, 0444, show_##_name, NULL)
> > +
> > +CPUINFO_ATTR_RO(midr);
> > +CPUINFO_ATTR_RO(revidr);
> 
> Since exposing these values is aimed at JIT code (and not human
> readable), wouldn't it make more sense to present the binary value
> instead of the ascii transformation?

Per Documentation/filesystems/sysfs.txt, attributes should be ASCII text
files, with one value per file. I think they should stay as they are.

Thanks,
Mark.