linux-kernel - Re: [PATCH 4/6] hwrng: st: Add support for ST's HW Random Number Generator

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Date:	Mon, 14 Sep 2015 08:42:34 +0100
From:	Lee Jones <lee.jones@...aro.org>
To:	Fabio Estevam <festevam@...il.com>
Cc:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Pankaj Dev <pankaj.dev@...com>, linux-crypto@...r.kernel.org,
	Matt Mackall <mpm@...enic.com>, kernel@...inux.com
Subject: Re: [PATCH 4/6] hwrng: st: Add support for ST's HW Random Number
 Generator

On Sat, 12 Sep 2015, Fabio Estevam wrote:

> On Fri, Sep 11, 2015 at 5:08 PM, Lee Jones <lee.jones@...aro.org> wrote:
> 
> > +       res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > +       base = devm_ioremap_resource(&pdev->dev, res);
> > +       if (IS_ERR(base))
> > +               return PTR_ERR(base);
> > +
> > +       clk = devm_clk_get(&pdev->dev, NULL);
> > +       if (!clk)
> > +               return -EINVAL;
> 
> This should be:
> 
>     if (IS_ERR(clk))
>         return PTR_ERR(clk);

You're right.  Will fix.

> > +
> > +       clk_prepare_enable(clk);
> 
> This may fail, so better check its return value and propagate it on error.

Looks like the jury is out on this one.

$ git grep clk_prepare_enable | grep '= clk\|if (' | wc -l
659
$ git grep clk_prepare_enable | grep -v '= clk\|if (' | wc -l
569

... but it's not a problem to fix up.  Will do.

> > +       ddata->ops.priv = (unsigned long)ddata;
> > +       ddata->ops.read = st_rng_read;
> > +       ddata->ops.name = pdev->name;
> > +       ddata->base     = base;
> > +       ddata->clk      = clk;
> > +
> > +       dev_set_drvdata(&pdev->dev, ddata);
> > +
> > +       ret = hwrng_register(&ddata->ops);
> > +       if (ret) {
> > +               dev_err(&pdev->dev, "Failed to register HW RNG\n");
> > +               return ret;
> > +       }
> > +
> > +       dev_info(&pdev->dev, "Successfully registered HW RNG\n");
> 
> No need to put this info.

Ah, you caught me!

I know these types of prints are usually deemed not useful; however,
unless there is a failure both this driver and the core driver are
silent, so the user doesn't know that 1 or more of these devices are
available.  I personally like to see an entry in the bootlog for this
kind of functionality.

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog
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