linux-kernel - Re: [PATCH -next] tpm: Use kzalloc for allocating only one thing

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Message-ID: <20210105055905.GA24455@kernel.org>
Date:   Tue, 5 Jan 2021 07:59:05 +0200
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     James Bottomley <James.Bottomley@...senPartnership.com>
Cc:     Zheng Yongjun <zhengyongjun3@...wei.com>, peterhuewe@....de,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
        jgg@...pe.ca
Subject: Re: [PATCH -next] tpm: Use kzalloc for allocating only one thing

On Tue, Dec 29, 2020 at 08:23:49AM -0800, James Bottomley wrote:
> On Tue, 2020-12-29 at 21:51 +0800, Zheng Yongjun wrote:
> > Use kzalloc rather than kcalloc(1,...)
> > 
> > The semantic patch that makes this change is as follows:
> > (http://coccinelle.lip6.fr/)
> 
> What's the reason for wanting to do this transformation?
> 
> >  drivers/char/tpm/tpm1-cmd.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/char/tpm/tpm1-cmd.c b/drivers/char/tpm/tpm1-
> > cmd.c
> > index ca7158fa6e6c..4d8415e3b778 100644
> > --- a/drivers/char/tpm/tpm1-cmd.c
> > +++ b/drivers/char/tpm/tpm1-cmd.c
> > @@ -794,7 +794,7 @@ int tpm1_pm_suspend(struct tpm_chip *chip, u32
> > tpm_suspend_pcr)
> >   */
> >  int tpm1_get_pcr_allocation(struct tpm_chip *chip)
> >  {
> > -	chip->allocated_banks = kcalloc(1, sizeof(*chip-
> > >allocated_banks),
> > +	chip->allocated_banks = kzalloc(sizeof(*chip->allocated_banks),
> >  					GFP_KERNEL);
> >  	if (!chip->allocated_banks)
> >  		return -ENOMEM;
> 
> The reason tpm1 has this is because it mirrors the allocation in tpm2
> so we retain code consistency.  It's a fairly minor advantage, so it
> could be changed if you have a better rationale ... but what is it?

Yup, I neither understand this.

> James

/Jarkko