netdev - Re: [PATCH v3 01/11] can: Add LIN bus as CAN abstraction

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Date: Wed, 8 May 2024 19:48:18 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Christoph Fritz <christoph.fritz@...dev.de>
Cc: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
	Oliver Hartkopp <socketcan@...tkopp.net>,
	Marc Kleine-Budde <mkl@...gutronix.de>,
	Jiri Slaby <jirislaby@...nel.org>,
	Vincent Mailhol <mailhol.vincent@...adoo.fr>,
	"David S . Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, Jiri Kosina <jikos@...nel.org>,
	Benjamin Tissoires <bentiss@...nel.org>,
	Sebastian Reichel <sre@...nel.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Andreas Lauser <andreas.lauser@...cedes-benz.com>,
	Jonathan Corbet <corbet@....net>,
	Pavel Pisa <pisa@....felk.cvut.cz>, linux-can@...r.kernel.org,
	Netdev <netdev@...r.kernel.org>, devicetree@...r.kernel.org,
	linux-input@...r.kernel.org,
	linux-serial <linux-serial@...r.kernel.org>
Subject: Re: [PATCH v3 01/11] can: Add LIN bus as CAN abstraction

On Wed, May 08, 2024 at 08:20:51PM +0200, Christoph Fritz wrote:
> ...
> > ...
> > > > > +static int lin_create_sysfs_id_files(struct net_device *ndev)
> > > > > +{
> > > > > +	struct lin_device *ldev = netdev_priv(ndev);
> > > > > +	struct kobj_attribute *attr;
> > > > > +	int ret;
> > > > > +
> > > > > +	for (int id = 0; id < LIN_NUM_IDS; id++) {
> > > > > +		ldev->sysfs_entries[id].ldev = ldev;
> > > > > +		attr = &ldev->sysfs_entries[id].attr;
> > > > > +		attr->attr.name = kasprintf(GFP_KERNEL, "%02x", id);
> > > > > +		if (!attr->attr.name)
> > > > > +			return -ENOMEM;
> > > > > +		attr->attr.mode = 0644;
> > > > > +		attr->show = lin_identifier_show;
> > > > > +		attr->store = lin_identifier_store;
> > > > > +
> > > > > +		sysfs_attr_init(&attr->attr);
> > > > > +		ret = sysfs_create_file(ldev->lin_ids_kobj, &attr->attr);
> > > > > +		if (ret) {
> > > > > +			kfree(attr->attr.name);
> > > > > +			return -ENOMEM;
> > > > > +		}
> > > > > +	}
> > > > > +
> > > > > +	return 0;
> > > > > +}
> > > > 
> > > > Can you use .dev_groups instead ?
> > > 
> > > I'm not sure where to attach this in this glue code here. Should I do a
> > > class_register() and add the .dev_groups there?
> > 
> > I guess struct class would be correct direction but I'm not sure if it's 
> > viable in this case. It would avoid the need for custom sysfs setup code
> > if it's workable.
> 
> I just tried to find a way, but these are 64 sysfs files and declaring
> them all static looks a bit odd to me. I might be missing something
> here.
> 
> For v4 I would stick to the dynamic setup and fix the rollback.
> 
> Any objections?

Yes, you race with userspace and loose by trying to do this "by hand".
Make this static please.

thanks,

greg k-h