linux-kernel - Re: [PATCH v2 3/4] switchtec: Add sysfs attributes to the Switchtec driver

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Message-ID: <7c981c0d-e7ff-bf28-ec55-cf5c39290437@deltatee.com>
Date:   Thu, 23 Feb 2017 15:56:21 -0700
From:   Logan Gunthorpe <logang@...tatee.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Keith Busch <keith.busch@...el.com>,
        Myron Stowe <myron.stowe@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Jonathan Corbet <corbet@....net>,
        "David S. Miller" <davem@...emloft.net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Emil Velikov <emil.l.velikov@...il.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Ryusuke Konishi <konishi.ryusuke@....ntt.co.jp>,
        Stefan Berger <stefanb@...ux.vnet.ibm.com>,
        Wei Zhang <wzhang@...com>,
        Kurt Schwemmer <kurt.schwemmer@...rosemi.com>,
        Stephen Bates <stephen.bates@...rosemi.com>,
        linux-pci@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/4] switchtec: Add sysfs attributes to the Switchtec
 driver



On 23/02/17 03:43 PM, Bjorn Helgaas wrote:
> This path seems a little generic.  I don't see other cases where a
> product brand name ("Switchtec") appears at the top level of
> /sys/class/...

Ok, well we are certainly open to suggestions, but there isn't really a
generic version of this device available so I'm not sure how we would
change that. Per device-type classes aren't that uncommon though, a
quick grep shows things like:

platform/chrome/cros_ec_dev.c:40:static struct class cros_class
s390/char/raw3270.h:94:extern struct class *class3270;
net/ethernet/hisilicon/hns/hnae.c:19:static struct class *hnae_class;
mfd/ucb1x00-core.c:490:static struct class ucb1x00_class

> My question is based on "ls Documentation/ABI/testing/sysfs-class*",
> not on any great knowledge of sysfs, and I see Greg has already given
> a Reviewed-by for this, so maybe this is the right approach.
> 
> It does seem like the path could include a clue that this is related
> to PCI.

I mean, we could change it to pci-switchtec or something if you think
that would be better..?? But I'm not sure how else to accommodate this.

> Is there a link to the switch PCI device itself, e.g., to
> /sys/devices/pci*?  Should these attributes simply be put in a
> subdirectory there, e.g., in
> 
>   /sys/devices/pci0000:00/0000:00:00.0/stats/...

Well our device shows up here in the tree:

/sys/devices/pci0000:00/0000:00:03.0/0000:03:00.1/switchtec/switchtec0

(Which userspace can get to by following the link at
/sys/class/switchtec/switchtec0) The switch is then always:

/sys/devices/pci0000:00/0000:00:03.0

Thanks,

Logan