linux-kernel - Re: [BUG, bisect, PATCH 04/10] tpm: move the PPI attributes to character device directory.

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Message-ID: <20151107025439.GA2911@newt.localdomain>
Date:	Fri, 6 Nov 2015 18:54:39 -0800
From:	Jeremiah Mahler <jmmahler@...il.com>
To:	Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
	tpmdd-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
	peterhuewe@....de, gregkh@...uxfoundation.org,
	jgunthorpe@...idianresearch.com, dhowells@...hat.com,
	artem.bityutskiy@...ux.intel.com,
	Marcel Selhorst <tpmdd@...horst.net>
Subject: Re: [BUG, bisect, PATCH 04/10] tpm: move the PPI attributes to
 character device directory.

Jarkko,

On Wed, Nov 04, 2015 at 10:17:05AM -0800, Jeremiah Mahler wrote:
> Jarkko, all,
> 
> On Fri, Oct 16, 2015 at 09:40:23PM +0300, Jarkko Sakkinen wrote:
> > Moved PPI attributes to the character device directory. This aligns with
> > the sysfs guidelines and makes them race free because they are created
> > atomically with the character device as part of device_register().The
> > character device and the sysfs attributes appear at the same time to the
> > user space.
> > 
> > As part of this change we enable PPI attributes also for TPM 2.0
> > devices. In order to retain backwards compatibility with TPM 1.x
> > devices, a symlink is created to the platform device directory.
> > 
> > Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
> > Reviewed-by: Jason Gunthorpe <jason.gunthorpe@...idianresearch.com>
> > Tested-by: Mimi Zohar <zohar@...ux.vnet.ibm.com> (on TPM 1.2)
> > Tested-by: Chris J Arges <chris.j.arges@...onical.com>
> > Tested-by: Colin Ian King <colin.king@...onical.com>
> > ---
> >  drivers/char/tpm/tpm-chip.c | 24 ++++++++++++++++--------
> >  drivers/char/tpm/tpm.h      | 17 ++++++-----------
> >  drivers/char/tpm/tpm_ppi.c  | 34 +++++++++++-----------------------
> >  3 files changed, 33 insertions(+), 42 deletions(-)
> > 
[...]
> > @@ -225,10 +220,20 @@ int tpm_chip_register(struct tpm_chip *chip)
> >  	if (rc)
> >  		return rc;
> >  
> > +	tpm_add_ppi(chip);
> > +
> >  	rc = tpm_dev_add_device(chip);
> >  	if (rc)
> >  		goto out_err;
> >  
> > +	if (!(chip->flags & TPM_CHIP_FLAG_TPM2)) {
> > +		rc = __compat_only_sysfs_link_entry_to_kobj(&chip->pdev->kobj,
> > +							    &chip->dev.kobj,
> > +							    "ppi");
> > +		if (rc)
> > +			goto out_err;
> > +	}
> > +

This new call to __compat_only_sysfs_link_entry_to_kobj fails on an Acer
C720 due to a failed call to kernfs_find_and_get (discussed in a second
message).

[...]
> 
> The commit for this patch (9b774d5cf2db4) present in the latest
> linux-next (20151101+) breaks suspend/resume on an Acer C720 Chromebook.
> The computer will successfully suspend but when a resume is attempted
> a blank screen is displayed for a few seconds and then it reboots.
> 
> -- 
> - Jeremiah Mahler

-- 
- Jeremiah Mahler
--
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