From: Michael Ellerman <mpe@ellerman.id.au>
To: Paul Mackerras <paulus@ozlabs.org>,
"Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: Paul Mackerras via Linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
Subject: Re: [RFC PATCH 7/9] powerpc/mm/book3s-64: Shuffle read, write, execute and user bits in PTE
Date: Mon, 22 Feb 2016 11:27:36 +1100 [thread overview]
Message-ID: <1456100856.4690.3.camel@ellerman.id.au> (raw)
In-Reply-To: <20160221223616.GB30309@fergus.ozlabs.ibm.com>
On Mon, 2016-02-22 at 09:36 +1100, Paul Mackerras wrote:
> On Sun, Feb 21, 2016 at 01:00:54PM +0530, Aneesh Kumar K.V wrote:
> > Paul Mackerras <paulus@samba.org> writes:
> >
> > Also can you use constants like
> > #define _PAGE_USER PPC_BIT(60)
>
> I'd really rather not - that is harder for the casual reader to parse,
> because they then have to go off and find out what exactly PPC_BIT
> does. The only time that using PPC_BIT would help is when checking
> that the bit definitions match the Power ISA, and that's presumably
> done by intelligent people that can handle backwards bit numbering in
> their heads. :)
Yep agree 100%.
Using PPC_BIT() means every time someone sees that defintion they need to think
about what the conversion is and whether it's right, ie. for the entire future
history of this code.
On the other hand not using PPC_BIT() means the person who writes the
definition needs to think about it and do the correct conversion, but only
once.
cheers
next prev parent reply other threads:[~2016-02-22 0:27 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-20 6:12 [RFC PATCH 0/9] powerpc/mm: Restructure Linux PTE on Book3S/64 to radix format Paul Mackerras
2016-02-20 6:12 ` [RFC PATCH 1/9] powerpc/mm/book3s-64: Clean up some obsolete or misleading comments Paul Mackerras
2016-02-20 6:12 ` [RFC PATCH 2/9] powerpc/mm/book3s-64: Free up 7 high-order bits in the Linux PTE Paul Mackerras
2016-02-20 16:16 ` Aneesh Kumar K.V
2016-02-21 22:43 ` Paul Mackerras
2016-02-20 6:12 ` [RFC PATCH 3/9] powerpc/mm/64: Use physical addresses in upper page table tree levels Paul Mackerras
2016-02-20 16:35 ` Aneesh Kumar K.V
2016-02-21 22:45 ` Paul Mackerras
2016-02-20 6:12 ` [RFC PATCH 4/9] powerpc/mm/book3s-64: Move _PAGE_PRESENT to the most significant bit Paul Mackerras
2016-02-20 8:33 ` kbuild test robot
2016-02-20 16:41 ` Aneesh Kumar K.V
2016-02-21 22:40 ` Paul Mackerras
2016-02-20 6:12 ` [RFC PATCH 5/9] powerpc/mm/book3s-64: Move _PAGE_PTE to 2nd " Paul Mackerras
2016-02-20 6:12 ` [RFC PATCH 6/9] powerpc/mm/book3s-64: Move HPTE-related bits in PTE to upper end Paul Mackerras
2016-02-20 6:12 ` [RFC PATCH 7/9] powerpc/mm/book3s-64: Shuffle read, write, execute and user bits in PTE Paul Mackerras
2016-02-21 7:30 ` Aneesh Kumar K.V
2016-02-21 22:36 ` Paul Mackerras
2016-02-22 0:27 ` Michael Ellerman [this message]
2016-02-20 6:12 ` [RFC PATCH 8/9] powerpc/mm/book3s-64: Move software-used " Paul Mackerras
2016-02-20 6:12 ` [RFC PATCH 9/9] powerpc/mm/book3s-64: Expand the real page number field of the Linux PTE Paul Mackerras
2016-02-20 14:40 ` [RFC PATCH 0/9] powerpc/mm: Restructure Linux PTE on Book3S/64 to radix format Aneesh Kumar K.V
2016-02-20 15:32 ` Aneesh Kumar K.V
2016-02-21 7:41 ` Aneesh Kumar K.V
2016-02-21 22:31 ` Paul Mackerras
2016-02-22 0:30 ` Michael Ellerman
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