linux-kernel - Re: [PATCH v7 17/17] PCI/AER: Add sysfs attributes for log ratelimits

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Message-ID: <20250521225942.GA1452275@bhelgaas>
Date: Wed, 21 May 2025 17:59:42 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Cc: linux-pci@...r.kernel.org, Jon Pan-Doh <pandoh@...gle.com>,
	Karolina Stolarek <karolina.stolarek@...cle.com>,
	Weinan Liu <wnliu@...gle.com>,
	Martin Petersen <martin.petersen@...cle.com>,
	Ben Fuller <ben.fuller@...cle.com>,
	Drew Walton <drewwalton@...rosoft.com>,
	Anil Agrawal <anilagrawal@...a.com>,
	Tony Luck <tony.luck@...el.com>,
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
	Sathyanarayanan Kuppuswamy <sathyanarayanan.kuppuswamy@...ux.intel.com>,
	Lukas Wunner <lukas@...ner.de>, Sargun Dhillon <sargun@...a.com>,
	"Paul E . McKenney" <paulmck@...nel.org>,
	Mahesh J Salgaonkar <mahesh@...ux.ibm.com>,
	Oliver O'Halloran <oohall@...il.com>,
	Kai-Heng Feng <kaihengf@...dia.com>,
	Keith Busch <kbusch@...nel.org>, Robert Richter <rrichter@....com>,
	Terry Bowman <terry.bowman@....com>,
	Shiju Jose <shiju.jose@...wei.com>,
	Dave Jiang <dave.jiang@...el.com>, linux-kernel@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org, Bjorn Helgaas <bhelgaas@...gle.com>,
	Krzysztof Wilczyński <kwilczynski@...nel.org>
Subject: Re: [PATCH v7 17/17] PCI/AER: Add sysfs attributes for log ratelimits

On Wed, May 21, 2025 at 11:46:00AM +0100, Jonathan Cameron wrote:
> On Tue, 20 May 2025 16:50:34 -0500
> Bjorn Helgaas <helgaas@...nel.org> wrote:
> 
> > From: Jon Pan-Doh <pandoh@...gle.com>
> > 
> > Allow userspace to read/write log ratelimits per device (including
> > enable/disable). Create aer/ sysfs directory to store them and any
> > future aer configs.
> ...

> There is some relatively new SYSFS infra that I think will help
> make this slightly nicer by getting rid of the extra directory when
> there is nothing to be done with it.

> > +#define aer_ratelimit_burst_attr(name, ratelimit)			\
> > +	static ssize_t							\
> > +	name##_show(struct device *dev, struct device_attribute *attr,	\
> > +		    char *buf)						\
> > +{									\
> 
> A little odd looking to indent this less than the line above.

Yep, fixed.

> > +const struct attribute_group aer_attr_group = {
> > +	.name = "aer",
> > +	.attrs = aer_attrs,
> > +	.is_visible = aer_attrs_are_visible,
> > +};
> 
> There are a bunch of macros to simplify cases where
> a whole group is either enabled or not and make the group
> itself go away if there is nothing to be shown.
> 
> DEFINE_SIMPLE_SYSFS_GROUP_VISIBLE() combined with
> SYSFS_GROUP_VISIBLE() around the assignment does what we
> want here I think.
> 
> Whilst we can't retrofit that stuff onto existing ABI
> as someone may be assuming directory presence, we can
> make sysfs less cluttered for new stuff.
> 
> Maybe I'm missing why that doesn't work here though!

Is this something we can fix later, or are we locking ourselves into
user-visible ABI that's hard to change?  I'm kind of against the wall
relative to the v6.16 merge window and haven't had time to dig into
this part.