linux-kernel - Re: [PATCH 1/2] hwrng: Add support for ASPEED RNG

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Date:   Mon, 03 Feb 2020 14:37:16 +1030
From:   "Andrew Jeffery" <andrew@...id.au>
To:     "Oscar A Perez" <linux@...ralgames.com>
Cc:     "Joel Stanley" <joel@....id.au>, "Matt Mackall" <mpm@...enic.com>,
        "Herbert Xu" <herbert@...dor.apana.org.au>,
        "Rob Herring" <robh+dt@...nel.org>,
        "Mark Rutland" <mark.rutland@....com>,
        "Linux Crypto Mailing List" <linux-crypto@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        "Linux ARM" <linux-arm-kernel@...ts.infradead.org>,
        linux-aspeed <linux-aspeed@...ts.ozlabs.org>,
        "Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] hwrng: Add support for ASPEED RNG

On Wed, 29 Jan 2020, at 10:56, linux@...ralgames.com wrote:
> On 2020-01-27 18:53, Andrew Jeffery wrote:
> > Not that I've looked, but is it feasible to augment timeriomem-rng with
> > the ability to configure the RNG rather than implement a new driver? 
> > Why
> > didn't you go that route?
> > 
> 
> I decided to wrote the Aspeed-RNG driver because was under the 
> impression that the community would prefer dedicated drivers over 
> generic ones for these SOCs. 

I think we should leverage existing work where we can. Lets not make
more extra for ourselves :)

> However, enhancing timeriomem-rng module 
> is not hard at all.  As I matter of fact, I'm currently testing changes 
> to timeriomem-rng and so far so good. If you would like to have a quick 
> look to my changes, I just pushed patches to the same repo a couple of 
> hours ago:  
> https://github.com/operezmuena/aspeed-rng-testing/tree/master/patches

I think this is a good approach  so long as we can create a clean interface
to the control MMIO(s) inside the driver, i.e. we shouldn't be baking any
Aspeed-specific information into generic sections of code. Usually this
means sticking a pointer to an ops struct in the data member of the
matching OF ID struct.

Input from the RNG maintainers will be helpful here.

Andrew