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

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Date:	Tue, 01 Mar 2011 19:21:47 -0800
From:	Saravana Kannan <skannan@...eaurora.org>
To:	Ryan Mallon <ryan@...ewatersys.com>
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>,
	Jouni Hogander <jouni.hogander@...ia.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>,
	Andrei Warkentin <andreiw@...orola.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 03/01/2011 07:11 PM, Ryan Mallon wrote:
> 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/.

Makes sense. We can drop the soc- prefix. So the contenders left: family 
vs <somethingelse>. Would still be nice if the other folks chime in.

>> 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? :-).

Ah, sorry. Didn't give enough details. To give some context, I manage 
the clock stuff for MSM. The MSM clock driver exports clock control thru 
debugfs. We have test scripts that bang the clocks to test them. Each 
SoC has a different set of "touch me and you die" clocks that the test 
script shouldn't mess with. This socinfo would be useful for those test 
cases.

>> * 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.

Hmm... didn't know USB devices/gadgets could be handled from userspace.

Thanks,
Saravana
-- 
Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.
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