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

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:

quoted

+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.

quoted

+	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