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

[Bjorn Helgaas]

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