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Message-ID: <fd20f4fae3d4bc1de0e62a25cead4db00bdd8dbd.camel@gmail.com>
Subject: Re: [PATCH v2 1/1] powerpc/iommu: Enable remaining IOMMU Pagesizes
 present in LoPAR
From:   Leonardo Bras <leobras.c@gmail.com>
To:     Segher Boessenkool <segher@kernel.crashing.org>,
        Alexey Kardashevskiy <aik@ozlabs.ru>
Cc:     Michael Ellerman <mpe@ellerman.id.au>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>, brking@linux.vnet.ibm.com,
        linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Date:   Wed, 14 Apr 2021 01:02:16 -0300
In-Reply-To: <20210412222143.GO26583@gate.crashing.org>
References: <20210407195613.131140-1-leobras.c@gmail.com>
         <87im4xe3pk.fsf@mpe.ellerman.id.au>
         <8e1ce7e9-415b-92ea-0437-a4331ed3c7f9@ozlabs.ru>
         <87ft01du50.fsf@mpe.ellerman.id.au>
         <21407a96-5b20-3fae-f1c8-895973b655ef@ozlabs.ru>
         <20210412222143.GO26583@gate.crashing.org>
Organization: IBM
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On Mon, 2021-04-12 at 17:21 -0500, Segher Boessenkool wrote:
> On Fri, Apr 09, 2021 at 02:36:16PM +1000, Alexey Kardashevskiy wrote:
> > On 08/04/2021 19:04, Michael Ellerman wrote:
> > > > > > +#define QUERY_DDW_PGSIZE_4K	0x01
> > > > > > +#define QUERY_DDW_PGSIZE_64K	0x02
> > > > > > +#define QUERY_DDW_PGSIZE_16M	0x04
> > > > > > +#define QUERY_DDW_PGSIZE_32M	0x08
> > > > > > +#define QUERY_DDW_PGSIZE_64M	0x10
> > > > > > +#define QUERY_DDW_PGSIZE_128M	0x20
> > > > > > +#define QUERY_DDW_PGSIZE_256M	0x40
> > > > > > +#define QUERY_DDW_PGSIZE_16G	0x80
> > > > > 
> > > > > I'm not sure the #defines really gain us much vs just putting the
> > > > > literal values in the array below?
> > > > 
> > > > Then someone says "uuuuu magic values" :) I do not mind either way. 
> > > > Thanks,
> > > 
> > > Yeah that's true. But #defining them doesn't make them less magic, if
> > > you only use them in one place :)
> > 
> > Defining them with "QUERY_DDW" in the names kinda tells where they are 
> > from. Can also grep QEMU using these to see how the other side handles 
> > it. Dunno.
> 
> And *not* defining anything reduces the mental load a lot.  You can add
> a comment at the single spot you use them, explaining what this is, in a
> much better way!
> 
> Comments are *good*.
> 
> 
> Segher

Thanks for the feedback Alexey, Michael and Segher!

I have sent a v3 for this patch. 
http://patchwork.ozlabs.org/project/linuxppc-dev/patch/20210408201915.174217-1-leobras.c@gmail.com/

Please let me know of your feedback in it.

Best regards,
Leonardo Bras