RE: [PATCH] tpm: Add sysfs interface to show TPM hardware version

["Li, Meng" <Meng.Li@windriver.com>]

> -----Original Message-----
> From: Jarkko Sakkinen [mailto:jarkko.sakkinen@linux.intel.com]
> Sent: Monday, March 13, 2017 7:49 PM
> To: Li, Meng
> Cc: linux-kernel@vger.kernel.org; peterhuewe@gmx.de;
> tpmdd@selhorst.net; jgunthorpe@obsidianresearch.com; tpmdd-
> devel@lists.sourceforge.net
> Subject: Re: [PATCH] tpm: Add sysfs interface to show TPM hardware
> version
> 
> On Mon, Mar 13, 2017 at 01:21:57PM +0800, Meng.Li@windriver.com wrote:
> > From: Limeng <Meng.Li@windriver.com>
> >
> > So far, there is not a sysfs interface for user space code to check
> > the TPM hardware version(TPM1.x or TPM2). So, add a file named
> > description in /sys/class/tpm/tpmX/ to show it.
> >
> > Signed-off-by: Meng Li <Meng.Li@windriver.com>
> > ---
> >  drivers/char/tpm/tpm-chip.c |   85
> +++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 85 insertions(+)
> >
> > diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> > index c406343..da2cd69 100644
> > --- a/drivers/char/tpm/tpm-chip.c
> > +++ b/drivers/char/tpm/tpm-chip.c
> 
> tpm-sysfs.c Probably makes sense to rename legacy group there as tpm1_

Thanks for this advice.

> 
> > @@ -36,6 +36,83 @@
> >  dev_t tpm_devt;
> >
> >  /**
> > + * show_description - sysfs interface for checking current TPM hardware
> version.
> > + * @dev:	pointer to tpm chip device
> > + * @attr:	unused
> > + * @buf:	char buffer to be filled with TPM hardware version info
> > + *
> > + * Provides sysfs interface for showing current TPM hardware version.
> > + */
> > +static ssize_t show_description(struct device *dev,
> > +		struct device_attribute *attr, char *buf)
> 
> family
> 
> > +{
> > +	struct tpm_chip *chip = (struct tpm_chip *)container_of(dev,struct
> tpm_chip,dev);
> > +	int ret;
> > +
> > +	if (chip->flags & TPM_CHIP_FLAG_TPM2)
> > +		ret = sprintf(buf, "TPM 2.0");
> > +	else
> > +		ret = sprintf(buf, "TPM 1.x");
> > +
> > +	return ret;
> > +}
> > +
> > +/**
> > + * store_description - interface for manually setting data.
> > + * @dev:	unused
> > + * @attr:	unused
> > + * @buf:	unused
> > + * @count:	unused
> > + *
> > + * There is not any process in this function, reserve for feature.
> > + */
> > +static ssize_t store_description(struct device *dev, struct
> device_attribute *attr,
> > +		const char *buf, size_t count)
> > +{
> > +	return count;
> > +}
> 
> What is this??
> 
> > +
> > +static struct device_attribute tpm_attrs[] = {
> > +	__ATTR(description, S_IRUGO | S_IWUSR, show_description,
> > +store_description), };
> > +
> > +/**
> > + * tpm_create_sysfs - Create tpm sysfs interface.
> > + * @dev:	pointer to tpm chip device
> > + *
> > + * Create sysfs interface for checking current TPM hardware version.
> > + */
> > +static int tpm_create_sysfs(struct device *dev) {
> > +	int r, t;
> > +
> > +	for (t = 0; t < ARRAY_SIZE(tpm_attrs); t++) {
> > +		r = device_create_file(dev, &tpm_attrs[t]);
> > +		if (r) {
> > +			dev_err(dev, "failed to create sysfs file\n");
> > +			return r;
> > +		}
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +/**
> > + * tpm_remove_sysfs - Remove tpm sysfs interface.
> > + * @dev:	pointer to tpm chip device
> > + *
> > + * Remove sysfs interface for checking current TPM hardware version.
> > + */
> > +static void tpm_remove_sysfs(struct device *dev) {
> > +	int  t;
> > +
> > +	for (t = 0; t < ARRAY_SIZE(tpm_attrs); t++) {
> > +		device_remove_file(dev, &tpm_attrs[t]);
> > +	}
> > +}
> > +
> > +/**
> >   * tpm_try_get_ops() - Get a ref to the tpm_chip
> >   * @chip: Chip to ref
> >   *
> > @@ -363,6 +440,13 @@ int tpm_chip_register(struct tpm_chip *chip)
> >  		return rc;
> >  	}
> >
> > +	rc = tpm_create_sysfs(&chip->dev);
> > +	if (rc) {
> > +		tpm_del_legacy_sysfs(chip);
> > +		tpm_chip_unregister(chip);
> > +		return rc;
> > +	}
> > +
> >  	return 0;
> >  }
> >  EXPORT_SYMBOL_GPL(tpm_chip_register);
> > @@ -382,6 +466,7 @@ int tpm_chip_register(struct tpm_chip *chip)
> >   */
> >  void tpm_chip_unregister(struct tpm_chip *chip)  {
> > +	tpm_remove_sysfs(&chip->dev);
> >  	tpm_del_legacy_sysfs(chip);
> >  	tpm_bios_log_teardown(chip);
> >  	tpm_del_char_device(chip);
> > --
> > 1.7.9.5
> 
> You should put the attributes to chip->groups instead of racy creation of
> them.

Thanks for your advice. It is more reasonable in to chip->groups.

Regards,
Limeng

> 
> /Jarkko