Re: [PATCH 1/4] mtd: Add sysfs attr to expose ECC stats

From: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
To: Brian Norris <computersforpeace@gmail.com>
Cc: "linux-mtd@lists.infradead.org" <linux-mtd@lists.infradead.org>,
	David Woodhouse <dwmw2@infradead.org>,
	"Gupta, Pekon" <pekon@ti.com>,
	Linux Kernel <linux-kernel@vger.kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: Re: [PATCH 1/4] mtd: Add sysfs attr to expose ECC stats
Date: Mon, 12 May 2014 23:26:14 -0300	[thread overview]
Message-ID: <20140513022614.GA1447@arch.cereza> (raw)
In-Reply-To: <20140513005053.GZ28907@ld-irv-0074>

On 12 May 05:50 PM, Brian Norris wrote:
> > There are some guidelines about attributes in 'Documentation/filesystems/sysfs.txt'
> > Though it's acceptable to put array of values of the "same type" in single sysfs file,
> > But I'm still not confident on having all members of 'struct ecc_stats' being
> > represented by single sysfs file
> [...]
> 
> I agree, it looks like the sysfs policy would recommend against putting
> distinct properties in the same file.
> 

OK...

> I'm not sure if /sys/block/<disk>/stat is a good example, as it does
> violate this policy. It also seems to have some historical baggage.
> 
> But there is potentially one good reason for putting this distinct
> information in a single file: if the information must be returned
> atomically. For disk stats, it might be important to get a consistent
> snapshot of the disk stats (or nearly so, with minimal locking
> overhead), which might change significantly between file accesses if
> we're doing half a dozen file queries instead.
> 
> This same reason may not apply to these ECC stats, since none of these
> ECC stats are likely to be changing concurrently.
> 

Right.

> So I personally might lean toward "one file per attribute" here.
> 

Yup, no problem. Greg, if you can confirm this it'd be great.

> > >> I hope this will still keep it machine readable.
> > >Well, this is not a debugfs entry, so I'm not sure we want to add such debug
> > >information. Anyone can take a look at the code and see what ecc_stats mean.
> 
> The code or (as suggested by Pekon) the documentation
> (Documentation/ABI/). Either way -- with a single 'ecc_stats' table, or
> with 4 separate files -- they need to be documented.
> 

Sure, will document in next round.
-- 
Ezequiel García, Free Electrons
Embedded Linux, Kernel and Android Engineering
http://free-electrons.com