linux-kernel - Re: [PATCHv5 0/3] Introduce the /proc/socinfo and use it to export OMAP data

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Message-ID: <4D6DB566.4090908@bluewatersys.com>
Date:	Wed, 02 Mar 2011 16:11:34 +1300
From:	Ryan Mallon <ryan@...ewatersys.com>
To:	Saravana Kannan <skannan@...eaurora.org>
CC:	ext Nishanth Menon <nm@...com>,
	ext Tony Lindgren <tony@...mide.com>,
	Peter De-Schrijver <Peter.De-Schrijver@...ia.com>,
	ext Linus Walleij <linus.walleij@...aro.org>,
	Ambresh <a0393775@...com>,
	Andrei Warkentin <andreiw@...orola.com>,
	Lee Jones <Lee.Jones@...aro.org>,
	Russell King <linux@....linux.org.uk>,
	Jonas ABERG <jonas.aberg@...ricsson.com>,
	ext Kevin Hilman <khilman@...prootsystems.com>,
	David Brown <davidb@...eaurora.org>,
	Maxime Coquelin <maxime.coquelin-nonst@...ricsson.com>,
	linux-arm-msm@...r.kernel.org, loic.pallardy@...ricsson.com,
	"eduardo.valentin@...ia.com" <eduardo.valentin@...ia.com>,
	Linux-OMAP <linux-omap@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Daniel Walker <dwalker@...eaurora.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Jouni Hogander <jouni.hogander@...ia.com>,
	Paul Mundt <lethal@...ux-sh.org>,
	"santosh.shilimkar@...com" <santosh.shilimkar@...com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCHv5 0/3] Introduce the /proc/socinfo and use it to export
 OMAP data

On 03/02/2011 03:55 PM, Saravana Kannan wrote:
> On 03/01/2011 06:41 PM, Ryan Mallon wrote:
>> On 03/02/2011 03:23 PM, Saravana Kannan wrote:
>>> I don't have any attachment to the "arch" file suggestion. If there is a
>>> better solution to identify the different implementations of socinfo
>>> without having to maintain some "unique id" list in the kernel, then I'm
>>> all for it. But cpuinfo is not it.
>>
>> Sorry I am confusing the 'arch' and 'mach' bits here. I definitely have
>> an objection to having an 'arch' file (i.e. ARM). A 'mach' (i.e. omap)
>> file makes a bit more sense, but should probably be called 'mach' rather
>> than 'arch' to avoid this confusion :-).
> 
> Sorry for the confusion. Sure, I don't care much for the filename as
> long as we can all agree on it. I care more about the content of the
> file (using names very close to xxxx in mach-xxxx). I like "soc-family"
> better since it's generic enough to not force, say omap3 and omap4, to
> report different values.
> 
> Linus Walleij, Eduardo, Maxime, Andrei,
> 
> Would like to hear your opinion on the file name (soc-family vs. mach vs
> <somethingelse>) and the path /sys/devices/system/soc/.

'family' sounds good. I don't think we need the 'soc-' prefix on
filenames if they are already in /sys/devices/system/soc/.

> 
> If we settle on this, may be it would be easier to get this through.
> 
>> I still think it is a solution in search of a problem though. What
>> userspace programs need to know what specific SoC they are on? My
>> feeling is that if userspace needs to know this information, then it is
>> probably dicking around with things that should be managed by the
>> kernel. Differences in available peripherals, etc can be determined by
>> looking at existing sysfs files.
> 
> I certainly have seen several use cases. Couple of easy examples:
> 
> * A lot of test scripts would find this very useful. For example, some
> clock (present is all/most MSMs) shouldn't be tested on some SOCs as it
> would lock up the system if you try to turn it off while the CPU is
> running.

I don't follow here. Do you mean a struct clk clock or something else?
Why is userspace allowed to disable a clock which will effectively hang
the system? :-).

> * Some of the user space tools might want to report different "product
> id/type" (nothing to do with USB, etc) depending on what SOC it is
> running on.

This makes more sense. It would actually be useful for custom USB
devices (gadget) which can be done from user space.

~Ryan

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