linux-kernel - Re: [PATCH v2 1/4] tpm: Implement tpm_chip_find() and tpm_chip

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Message-Id: <5acee904-ede6-d33f-33b7-3ad94fce9850@linux.vnet.ibm.com>
Date:   Wed, 20 Jun 2018 17:13:01 -0400
From:   Stefan Berger <stefanb@...ux.vnet.ibm.com>
To:     Jason Gunthorpe <jgg@...pe.ca>
Cc:     linux-integrity@...r.kernel.org, jarkko.sakkinen@...ux.intel.com,
        zohar@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/4] tpm: Implement tpm_chip_find() and tpm_chip_put()
 for other subsystems

On 06/20/2018 04:50 PM, Jason Gunthorpe wrote:
> On Wed, Jun 20, 2018 at 04:42:33PM -0400, Stefan Berger wrote:
>> Implement tpm_chip_find() for other subsystems to find a TPM chip and
>> get a reference to that chip. Once done with using the chip, the reference
>> is released using tpm_chip_put().
>>
>> Signed-off-by: Stefan Berger <stefanb@...ux.vnet.ibm.com>
>>   drivers/char/tpm/tpm-chip.c | 37 +++++++++++++++++++++++++++++++++++++
>>   include/linux/tpm.h         |  9 +++++++++
>>   2 files changed, 46 insertions(+)
>>
>> diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
>> index 0a62c19937b6..eaaf41ce73d8 100644
>> +++ b/drivers/char/tpm/tpm-chip.c
>> @@ -81,6 +81,43 @@ void tpm_put_ops(struct tpm_chip *chip)
>>   EXPORT_SYMBOL_GPL(tpm_put_ops);
>>   
>>   /**
>> + * tpm_chip_put() - Release a ref to the tpm_chip
>> + * @chip: Chip to put
>> + */
>> +void tpm_chip_put(struct tpm_chip *chip)
>> +{
>> +	if (chip)
>> +		put_device(&chip->dev);
> Rarely like to see those if's inside a put function.. Does it actually
> help anything?
Following put_device() 'pattern' here which also checks using 'if (dev)'.

     Stefan