linux-kernel - Re: [PATCH v1 3/5] char: tpm: rewrite "tpm_tis_req

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Date:   Mon, 11 Nov 2019 20:25:40 -0500
From:   Stefan Berger <stefanb@...ux.ibm.com>
To:     amirmizi6@...il.comg, Stefan Berger <stefanb@...ux.vnet.ibm.com>,
        Eyal.Cohen@...oton.com, jarkko.sakkinen@...ux.intel.com,
        oshrialkoby85@...il.com, alexander.steffen@...ineon.com,
        robh+dt@...nel.org, mark.rutland@....com, peterhuewe@....de,
        jgg@...pe.ca, arnd@...db.de, gregkh@...uxfoundation.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-integrity@...r.kernel.org, oshri.alkoby@...oton.com,
        tmaimon77@...il.com, gcwilson@...ibm.com, kgoldman@...ibm.com,
        ayna@...ux.vnet.ibm.com, Dan.Morav@...oton.com,
        oren.tanami@...oton.com, shmulik.hagar@...oton.com,
        amir.mizinski@...oton.com
Subject: Re: [PATCH v1 3/5] char: tpm: rewrite "tpm_tis_req_canceled()"

On 11/10/19 1:00 PM, Jerry Snitselaar wrote:
> On Sun Nov 10 19, amirmizi6@...il.com wrote:
>> From: Amir Mizinski <amirmizi6@...il.com>
>>
>> using this function while read/write data resulted in aborted operation.
>> after investigating according to TCG TPM Profile (PTP) Specifications,
>> i found cancel should happen only if TPM_STS.commandReady bit is lit
>> and couldn't find a case when the current condition is valid.
>> also only cmdReady bit need to be compared instead of the full lower 
>> status register byte.
>>
>> Signed-off-by: Amir Mizinski <amirmizi6@...il.com>
>> ---
>> drivers/char/tpm/tpm_tis_core.c | 12 +-----------
>> 1 file changed, 1 insertion(+), 11 deletions(-)
>>
>> diff --git a/drivers/char/tpm/tpm_tis_core.c 
>> b/drivers/char/tpm/tpm_tis_core.c
>> index ce7f8a1..9016f06 100644
>> --- a/drivers/char/tpm/tpm_tis_core.c
>> +++ b/drivers/char/tpm/tpm_tis_core.c
>> @@ -627,17 +627,7 @@ static int probe_itpm(struct tpm_chip *chip)
>>
>> 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));
>
> Stefan were these cases you found that were deviating from the spec? 
> Wondering
> if dropping these will cause issues for these devices.


I believe these devices needed special handling of the status register 
as they didn't behave as the 'other' devices, so I would expect issues.

    Stefan