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

From: Greg Kroah-Hartman <[email-masked]>
Date: Wed, 8 May 2024 19:48:18 +0100

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