RE: [PATCH v5 2/3] hw_random: cctrng: introduce Arm CryptoCell driver

[Hadar Gat <Hadar.Gat@arm.com>]

Hi Rouven,

> 
> Hello Hadar,
> 
> On Sun, 2020-03-22 at 17:31 +0200, Hadar Gat wrote:
> > Introduce low level Arm CryptoCell TRNG HW support.
> >
> > Signed-off-by: Hadar Gat <hadar.gat@arm.com>
> > ---
> >  drivers/char/hw_random/Kconfig  |  12 +
> >  drivers/char/hw_random/Makefile |   1 +
> >  drivers/char/hw_random/cctrng.c | 735
> > ++++++++++++++++++++++++++++++++++++++++
> >  drivers/char/hw_random/cctrng.h |  69 ++++
> >  4 files changed, 817 insertions(+)
> >  create mode 100644 drivers/char/hw_random/cctrng.c  create mode
> > 100644 drivers/char/hw_random/cctrng.h
> >
> > [...]
> > +static int cctrng_probe(struct platform_device *pdev) {
> > +	struct resource *req_mem_cc_regs = NULL;
> > +	struct cctrng_drvdata *drvdata;
> > +	struct device *dev = &pdev->dev;
> > +	int rc = 0;
> > +	u32 val;
> > +	int irq;
> > +
> > +	drvdata = devm_kzalloc(dev, sizeof(*drvdata), GFP_KERNEL);
> > +	if (!drvdata)
> > +		return -ENOMEM;
> > +
> > +	drvdata->rng.name = devm_kstrdup(dev, dev_name(dev),
> > GFP_KERNEL);
> > +	if (!drvdata->rng.name)
> > +		return -ENOMEM;
> > +
> > +	drvdata->rng.read = cctrng_read;
> > +	drvdata->rng.priv = (unsigned long)drvdata;
> 
> You are not initializing drvdata->rng.quality to a default value, which results in
> the TRNG not being used by the kernel by default. If its a perfect TRNG this
> should be set to 1024, i.e. 1024 bits of entropy per
> 1024 bits of input.

Thanks for noticing. I'll fix that.

> 
> Regards,
> Rouven Czerwinski

Thanks,
Hadar