Re: [PATCH] tpm: Add flag to use default cancellation policy

[Eddie James]

On 9/8/22 00:22, Jarkko Sakkinen wrote:
> On Wed, Sep 07, 2022 at 11:43:17AM -0500, Eddie James wrote:
> > The check for cancelled request depends on the VID of the chip, but
> > some chips share VID which shouldn't share their cancellation
> > behavior. This is the case for the Nuvoton NPCT75X, which should use
> > the default cancellation check, not the Winbond one.
> > To avoid changing the existing behavior, add a new flag to indicate
> > that the chip should use the default cancellation check and set it
> > for the I2C TPM2 TIS driver.
> >
> > Signed-off-by: Eddie James <eajames@xxxxxxxxxxxxx>
> > ---
> >   drivers/char/tpm/tpm_tis_core.c | 18 ++++++++++--------
> >   drivers/char/tpm/tpm_tis_core.h |  1 +
> >   drivers/char/tpm/tpm_tis_i2c.c  |  1 +
> >   3 files changed, 12 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
> > index 757623bacfd5..175e75337395 100644
> > --- a/drivers/char/tpm/tpm_tis_core.c
> > +++ b/drivers/char/tpm/tpm_tis_core.c
> > @@ -682,15 +682,17 @@ static bool tpm_tis_req_canceled(struct tpm_chip *chip, u8 status)
> >   {
> >   	struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
> >   
> > -	switch (priv->manufacturer_id) {
> > -	case TPM_VID_WINBOND:
> > -		return ((status == TPM_STS_VALID) ||
> > -			(status == (TPM_STS_VALID | TPM_STS_COMMAND_READY)));
> > -	case TPM_VID_STM:
> > -		return (status == (TPM_STS_VALID | TPM_STS_COMMAND_READY));
> > -	default:
> > -		return (status == TPM_STS_COMMAND_READY);
> > +	if (!test_bit(TPM_TIS_DEFAULT_CANCELLATION, &priv->flags)) {
> > +		switch (priv->manufacturer_id) {
> > +		case TPM_VID_WINBOND:
> > +			return ((status == TPM_STS_VALID) ||
> > +				(status == (TPM_STS_VALID | TPM_STS_COMMAND_READY)));
> > +		case TPM_VID_STM:
> > +			return (status == (TPM_STS_VALID | TPM_STS_COMMAND_READY));
> > +		}
> Why there is no default: ?


Well I didn't want to duplicate the line "status == 
TPM_STS_COMMAND_READY" in the default case and for the flagged case. So 
now the switch just falls through for default. I can add default: break 
instead


> >   	}
> > +
> > +	return status == TPM_STS_COMMAND_READY;
> >   }
> >   
> >   static irqreturn_t tis_int_handler(int dummy, void *dev_id)
> > diff --git a/drivers/char/tpm/tpm_tis_core.h b/drivers/char/tpm/tpm_tis_core.h
> > index 66a5a13cd1df..b68479e0de10 100644
> > --- a/drivers/char/tpm/tpm_tis_core.h
> > +++ b/drivers/char/tpm/tpm_tis_core.h
> > @@ -86,6 +86,7 @@ enum tis_defaults {
> >   enum tpm_tis_flags {
> >   	TPM_TIS_ITPM_WORKAROUND		= BIT(0),
> >   	TPM_TIS_INVALID_STATUS		= BIT(1),
> > +	TPM_TIS_DEFAULT_CANCELLATION	= BIT(2),
> >   };
> >   
> >   struct tpm_tis_data {
> > diff --git a/drivers/char/tpm/tpm_tis_i2c.c b/drivers/char/tpm/tpm_tis_i2c.c
> > index 0692510dfcab..6722588e0217 100644
> > --- a/drivers/char/tpm/tpm_tis_i2c.c
> > +++ b/drivers/char/tpm/tpm_tis_i2c.c
> > @@ -329,6 +329,7 @@ static int tpm_tis_i2c_probe(struct i2c_client *dev,
> >   	if (!phy->io_buf)
> >   		return -ENOMEM;
> >   
> > +	set_bit(TPM_TIS_DEFAULT_CANCELLATION, &phy->priv.flags);
> What if you just zeroed manufacturer ID?


It's already zero there, and gets set to the VID as part of the core 
init function.


Thanks,

Eddie


> >   	phy->i2c_client = dev;
> >   
> >   	/* must precede all communication with the tpm */
> > --
> > 2.31.1
> BR, Jarkko