linux-kernel - Re: [RFC v4 17/25] powerpc, fbdev: Use arch_nvram_ops methods instead of nvram_read_byte() and nvram_write

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Date:	Fri, 18 Sep 2015 18:17:30 +1000 (AEST)
From:	Finn Thain <fthain@...egraphics.com.au>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
cc:	linux-kernel@...r.kernel.org, linux-m68k@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org, Paul Mackerras <paulus@...ba.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	Arnd Bergmann <arnd@...db.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Tomi Valkeinen <tomi.valkeinen@...com>,
	linux-fbdev@...r.kernel.org
Subject: Re: [RFC v4 17/25] powerpc, fbdev: Use arch_nvram_ops methods instead
 of nvram_read_byte() and nvram_write_byte()

Hi Ben,

On Thu, 16 Jul 2015, I wrote:

> On Wed, 15 Jul 2015, I wrote:
> 
> > On Tue, 14 Jul 2015, Benjamin Herrenschmidt wrote:
> > 
> > > Maybe we should have a dedicated accessor for "mac_xpram" ...
> > 
> ...
> 
> The arch_nvram_ops methods don't deal with structures like partitions ...

Instead of the accessor you suggested, perhaps it would be better to add a 
method like arch_nvram_ops.get_partition, to replace the 
pmac_get_partition() exported function?

The call sites for pmac_get_partition() are in the implementation of the 
IOC_NVRAM_GET_OFFSET ioctl that's used with /dev/nvram, and in 
pmac_xpram_read(). pmac_xpram_write() has no caller and could be removed.

But this doesn't have much to do with linux-fbdev. I think the old 
NV_CMODE/NV_VMODE issues*, which this patch avoids, are irrelevant to the 
problem of nvram module re-use, which is the aim of this patch series.

But if those issues really are relevant then we should move the discussion 
to the revised patch, that is, [RFC v6 16/25] powerpc, fbdev: Use NV_CMODE 
and NV_VMODE only when CONFIG_PPC32 and CONFIG_PPC_PMAC and CONFIG_NVRAM.

(There was no response to any patch in RFC v6 from any PowerPC 
maintainers, which is why I've revived this thread.)

* https://lists.ozlabs.org/pipermail/linuxppc-dev/2001-November/012662.html

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