Re: [PATCH v3 4/6] tpm: TPM 2.0 sysfs attributes

[Jarkko Sakkinen <jarkko.sakkinen-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>]

On Thu, Oct 16, 2014 at 11:31:46AM +0200, Greg KH wrote:
> On Wed, Oct 15, 2014 at 01:35:14PM +0200, Jarkko Sakkinen wrote:
> > +int tpm2_sysfs_add_device(struct tpm_chip *chip)
> > +{
> > +	struct pcr_bank *pcr_bank;
> > +	struct kobject *pcrs_kobj;
> > +	struct device *dev = chip->dev;
> > +	int rc;
> > +
> > +	rc = sysfs_create_group(&chip->vendor.miscdev.this_device->kobj,
> > +				&tpm_dev_group);
> > +	if (rc) {
> > +		dev_err(dev, "failed to create sysfs attributes, %d\n", rc);
> > +		return rc;
> > +	}
> 
> You just raced and created sysfs files _after_ userspace saw that your
> device was enabled.

Here the options are limited because misc_register already spawns
KOBJ_ADD. Not much to do unless we would wipe the current use of 
misc driver completely.

> 
> > +	pcrs_kobj = kobject_create_and_add("pcrs",
> > +					   &chip->vendor.miscdev.this_device->kobj);
> 
> Ick, no no no no.  Never create a kobject under a 'struct device'.  You
> just lost all libudev support for any attribute you created under here,
> not good at all.  Use a "real" device if you really want a sub-device,
> not a kobject.

Ack, will rework this.

> thanks,
> 
> greg k-h

/Jarkko