lkml.org 
[lkml]   [2018]   [Feb]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] char: nvram: disable on ARM
On 06/02/2018 at 23:55:02 +0100, Arnd Bergmann wrote:
> * arch/arm/kernel/time.c has this code
>
> #if defined(CONFIG_RTC_DRV_CMOS) || defined(CONFIG_RTC_DRV_CMOS_MODULE) || \
> defined(CONFIG_NVRAM) || defined(CONFIG_NVRAM_MODULE)
> /* this needs a better home */
> DEFINE_SPINLOCK(rtc_lock);
> EXPORT_SYMBOL(rtc_lock);
> #endif /* pc-style 'CMOS' RTC support */
>
> That can be adapted now, or maybe we could move all definitions into
> a common place (that needs some more planning).
>

Yes, on arm, the rtc_lock is mostly there to please
drivers/rtc/rtc-cmos.c. Maybe we could make the locking in this driver
x86 and PPC specific.

If we can get rid of arch/powerpc/platforms/chrp/time.c and
arch/powerpc/platforms/maple/time.c (so much duplicated code), then it
is x86 only.

> * similarly, this line in nvram.c can be simplified:
> #if defined(CONFIG_ATARI)
> # define MACH ATARI
> #elif defined(__i386__) || defined(__x86_64__) || defined(__arm__) /* and ?? */
> # define MACH PC
> #else
> # error Cannot build nvram driver for this machine configuration.
> #endif
>
> * GENERIC_NVRAM is not really generic, instead this seems to be the
> chardev that is used for 32-bit powerpc (powermac, 85xx, 86xx), while
> 64-bit powerpc (cell, maple, opal, pseries) use code from
> arch/powerpc/kernel/nvram_64.c, with the same underlying arch hooks.
> The nvram_64 code appears to be mostly a superset of the 32-bit
> generic_nvram one.
>
> * The code in drivers/char/nvram is not used at all when
> GENERIC_NVRAM is set, and half the code in there is different
> between x86 and atari.
>
> * most of the external interface in include/linux/nvram.h is
> unused, the rest tends to be architecture specific
>
> * The procfs file appears to be completely useless on any 64-bit
> x86 machine, this is what I see:
>
> $ cat /proc/driver/nvram
> Checksum status: valid
> # floppies : 0
> Floppy 0 type : none
> Floppy 1 type : none
> HD 0 type : none
> HD 1 type : none
> HD type 48 data: 0/0/0 C/H/S, precomp 0, lz 0
> HD type 49 data: 156/0/0 C/H/S, precomp 0, lz 0
> DOS base memory: 635 kB
> Extended memory: 65535 kB (configured), 65535 kB (tested)
> Gfx adapter : EGA, VGA, ... (with BIOS)
> FPU : not installed
>

I really don't think anyone is using that but I don't really know much
about x86 and the specification this may be part of.

I see the info may be used in drivers/video/fbdev/ and
drivers/platform/x86/thinkpad_acpi.c

--
Alexandre Belloni, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
http://bootlin.com

\
 
 \ /
  Last update: 2018-02-07 02:55    [W:0.079 / U:3.324 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site