linux-kernel - Re: [PATCH v9 00/22] Re-use nvram module

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Message-ID: <20190122092234.GA15813@kroah.com>
Date:   Tue, 22 Jan 2019 10:22:34 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Finn Thain <fthain@...egraphics.com.au>
Cc:     Arnd Bergmann <arnd@...db.de>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Michael Schmitz <schmitzmic@...il.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Joshua Thompson <funaho@...ai.org>,
        linux-kernel@...r.kernel.org, linux-m68k@...ts.linux-m68k.org,
        linuxppc-dev@...ts.ozlabs.org, linux-scsi@...r.kernel.org,
        linux-fbdev@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v9 00/22] Re-use nvram module

On Tue, Jan 15, 2019 at 03:18:56PM +1100, Finn Thain wrote:
> The "generic" NVRAM module, drivers/char/generic_nvram.c, implements a
> /dev/nvram misc device. This module is used only by 32-bit PowerPC
> platforms.
> 
> The RTC "CMOS" NVRAM module, drivers/char/nvram.c, also implements a
> /dev/nvram misc device. This module is now used only by x86 and m68k
> thanks to commit 3ba9faedc180 ("char: nvram: disable on ARM").
> 
> The "generic" module cannot be used by x86 or m68k platforms because it
> cannot co-exist with the "CMOS" module. One reason for that is the
> CONFIG_GENERIC_NVRAM kludge in drivers/char/Makefile. Another reason is
> that automatically loading the appropriate module would be impossible
> because only one module can provide the char-major-10-144 alias.
> 
> A multi-platform kernel binary needs a single, generic module. With this
> patch series, drivers/char/nvram.c becomes more generic and some of the
> arch-specific code gets moved under arch/. The nvram module is then
> usable by all m68k, powerpc and x86 platforms.
> 
> This allows for removal of drivers/char/generic_nvram.c as well as a
> duplicate in arch/powerpc/kernel/nvram_64.c. By reducing the number of
> /dev/nvram char misc device implementations, the number of bugs and
> inconsistencies is also reduced.
> 
> This approach reduces inconsistencies between PPC32 and PPC64 and also
> between PPC_PMAC and MAC. A uniform API has benefits for userspace.
> 
> For example, some error codes for some ioctl calls become consistent
> across PowerPC platforms. The uniform API can potentially benefit any
> bootloader that works across the various platforms having XPRAM
> (e.g. Emile).
> 
> This patch series was tested on Atari, Mac, PowerMac (both 32-bit and
> 64-bit) and ThinkPad hardware. AFAIK, it has not yet been tested on
> pSeries or CHRP.
> 
> I think there are two possible merge strategies for this patch series.
> The char misc maintainer could take the entire series. Alternatively,
> the m68k maintainer could take patches 1 thru 16 (though some of these
> have nothing to do with m68k) and after those patches reach mainline
> the powerpc maintainer could take 17 thru 22.

I just took the whole series, thanks for doing this, looks good.

greg k-h