linux-kernel - Re: [tpmdd-devel] [PATCH v1 12/12] tpm: TPM2 sysfs attributes

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Date:	Wed, 24 Sep 2014 22:39:41 +0200
From:	Peter Hüwe <PeterHuewe@....de>
To:	tpmdd-devel@...ts.sourceforge.net
Cc:	Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
	Stefan Berger <stefanb@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [tpmdd-devel] [PATCH v1 12/12] tpm: TPM2 sysfs attributes

Am Mittwoch, 24. September 2014, 19:59:40 schrieb Jason Gunthorpe:
> On Wed, Sep 24, 2014 at 01:34:11PM -0400, Stefan Berger wrote:
> > On 09/24/2014 01:13 PM, Jason Gunthorpe wrote:
> > >On Wed, Sep 24, 2014 at 12:06:02PM +0300, Jarkko Sakkinen wrote:
> > >>+static ssize_t durations_show(struct device *dev, struct
> > >>device_attribute *attr, +			      char *buf)
> > >>+{
> > >>+	struct tpm_chip *chip = dev_get_drvdata(dev);
> > >>+
> > >>+	if (chip->vendor.duration[TPM_LONG] == 0)
> > >>+		return 0;
> > >>+
> > >>+	return sprintf(buf, "%d %d %d [%s]\n",
> > >>+		       jiffies_to_usecs(chip->vendor.duration[TPM_SHORT]),
> > >>+		       jiffies_to_usecs(chip->vendor.duration[TPM_MEDIUM]),
> > >>+		       jiffies_to_usecs(chip->vendor.duration[TPM_LONG]),
> > >>+		       chip->vendor.duration_adjusted
> > >>+		       ? "adjusted" : "original");
> > >>+}
> > >>+static DEVICE_ATTR_RO(durations);
> > >
> > >Seem useless since the durations are constant, drop it?
> > 
> > We show them for TPM 1.2 as well, so I'd keep them fo TPM2.
> 
> The durations are constant and hardwired in the driver for TPM2, and
> the sysfs file format does not follow the one-value-per-file
> rule.
> 
> So it doesn't display anything useful. In TPM2 mode all the timeouts
> are constant and known, so I'd rather see it go away.


If it is more or less a no-op since we have set chip-
>vendor.duration[TPM_SHORT] for other code to work, we can show the values for 
TPM2.0.

However I think we don't need any extra code to show or hide the sysfs files 
for TPM2.0.

Peter
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