linux-kernel - Re: [PATCH 2/5] char: tile-srom: Remove reference to platform

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <5400C9C1.4060904@tilera.com>
Date:	Fri, 29 Aug 2014 14:43:13 -0400
From:	Chris Metcalf <cmetcalf@...era.com>
To:	Pawel Moll <pawel.moll@....com>
CC:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Olof Johansson <olof@...om.net>,
	Stephen Warren <swarren@...dotorg.org>,
	Catalin Marinas <Catalin.Marinas@....com>,
	"paul@...an.com" <paul@...an.com>, Arnd Bergmann <arnd@...db.de>,
	Peter De Schrijver <pdeschrijver@...dia.com>,
	"arm@...nel.org" <arm@...nel.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/5] char: tile-srom: Remove reference to platform_bus

(Resending with text/plain.)

First, sorry for the delayed response, with summer vacation and then
trying to catch up.  :-)

On 8/8/2014 12:34 PM, Pawel Moll wrote:
> On Tue, 2014-08-05 at 21:08 +0100, Chris Metcalf wrote:
>>>> In addition, we also have user binaries
>>>> in the wild that know to look for /sys/devices/platform/srom/ paths,
>>>> so I'm pretty reluctant to change this path without good reason.
>>> So what is the srom class for then if not for device discovery? And why
>>> do they look for them in the first place? To get relevant character
>>> device's data, if I understand it right?
>>>
>>> Maybe you could just register a simple "proper" platform device for all
>>> the sroms and then hang the class devices from it? I can type some code
>>> doing this if it sound reasonably?
>> By "device discovery" I meant the way you find the way in your devices
>> in /sysfs. You seem to be traversing /sys/devices/... tree, while you've
>> got almost direct access to them through /sys/class/srom and you can (I
>> believe, correct me if I'm wrong, Greg) rely on this path being stable.

Yes, this is an excellent point.  I will change the user tool to use
/sys/class instead and then it will work with the existing kernel as well
as with future kernels that incorporate your suggested change.

>> The
>> subdirectories under /sys/devices/platform/srom/ correspond to partitions
>> in the SPI-ROM, which are software constructs created by the Tilera hypervisor.
>> By default we have three, where the first holds boot data that the chip
>> can use to boot out of hardware, and the other two are smaller partitions
>> for boot- and user-specific data.  We use the /sys files primarily to get the
>> page size and sector size for the sroms, and also export other interesting
>> information like the total size of the particular srom device.
>>
>> Thank you for volunteering to write a bit of code; if that's the best
>> way to clarify this for us, fantastic, or else pointing us at existing
>> good practices or documentation would be great too.
> [...]
> @@ -350,7 +351,7 @@ static int srom_setup_minor(struct srom_dev *srom, int index)
>  		       SROM_PAGE_SIZE_OFF, sizeof(srom->page_size)) < 0)
>  		return -EIO;
>
> -	dev = device_create(srom_class, &platform_bus,
> +	dev = device_create(srom_class, srom_parent,
>  			    MKDEV(srom_major, index), srom, "%d", index);
>  	return PTR_ERR_OR_ZERO(dev);
>  }

The second argument should be &srom_parent.dev though, I think.  Right?

> Would that work for you? Note that it will move the srom class devices
> one level deeper in /sys/devices/... hierarchy.

Yes, that seems slightly unfortunately but not too problematic.  If the
consensus is that this is the way to go, I can certainly take this change
into the Tile tree.

-- 
Chris Metcalf, Tilera Corp.
http://www.tilera.com


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/