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
