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

From: Bjorn Helgaas <helgaas@kernel.org>
To: Logan Gunthorpe <logang@deltatee.com>
Cc: Keith Busch <keith.busch@intel.com>,
	Myron Stowe <myron.stowe@gmail.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Bjorn Helgaas <bhelgaas@google.com>,
	Geert Uytterhoeven <geert+renesas@glider.be>,
	Jonathan Corbet <corbet@lwn.net>,
	"David S. Miller" <davem@davemloft.net>,
	Andrew Morton <akpm@linux-foundation.org>,
	Emil Velikov <emil.l.velikov@gmail.com>,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	Guenter Roeck <linux@roeck-us.net>,
	Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
	Linus Walleij <linus.walleij@linaro.org>,
	Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>,
	Stefan Berger <stefanb@linux.vnet.ibm.com>,
	Wei Zhang <wzhang@fb.com>,
	Kurt Schwemmer <kurt.schwemmer@microsemi.com>,
	Stephen Bates <stephen.bates@microsemi.com>,
	linux-pci@vger.kernel.org, linux-doc@vger.kernel.org,
	linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 3/4] switchtec: Add sysfs attributes to the Switchtec driver
Date: Fri, 24 Feb 2017 16:45:27 -0600	[thread overview]
Message-ID: <20170224224527.GC26430@bhelgaas-glaptop.roam.corp.google.com> (raw)
In-Reply-To: <7c981c0d-e7ff-bf28-ec55-cf5c39290437@deltatee.com>

On Thu, Feb 23, 2017 at 03:56:21PM -0700, Logan Gunthorpe wrote:
> 
> 
> 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.

I'm OK with it as-is.

> > 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

That's exactly what I was looking for; I just didn't realize it was
connected like this.

Bjorn