Re: [brgl:gpio/for-next 42/47] gpio-mmio.c:undefined reference to `iowrite64'

[Andy Shevchenko <andy.shevchenko@xxxxxxxxx>]

On Sat, Feb 24, 2024 at 8:57 PM Bartosz Golaszewski <brgl@xxxxxxxx> wrote:
> On Sat, Feb 24, 2024 at 4:58 PM Linus Walleij <linus.walleij@xxxxxxxxxx> wrote:
> > On Fri, Feb 23, 2024 at 1:44 PM kernel test robot <lkp@xxxxxxxxx> wrote:
> >
> > > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/brgl/linux.git gpio/for-next
> > > head:   7bb5f3a7ca8856c5c1fa26a6e3f58a1254019dc0
> > > commit: 36e44186e0badfda499b65d4462c49783bf92314 [42/47] gpio: mmio: Support 64-bit BE access
> > > config: um-allyesconfig (https://download.01.org/0day-ci/archive/20240223/202402232058.4eDf4GRs-lkp@xxxxxxxxx/config)
> >
> > UM Linux now again.
> >
> > gpio-mmio depends on HAS_IOMEM
> > and UM Linux has set HAS_IOMEM, but
> > also claims to support 64bit without providing the necessary 64bit
> > io-accessors.
> >
> > Maybe UM Linux need to be fixed?
>
> Nah, there were other reports for the same issues, at least for x86
> and alpha. I hope Andy will have some time to look into it early this
> week, otherwise we'll have to revert the offending patch.

So, the problem is that those architectures do define GENERIC_IOMAP
which does NOT have implementations of ioread64*()/iowrite64*(). And
we have dead code like drivers/vfio/pci/vfio_pci_rdwr.c (the part
related to 64-bit IO accessors), which nobody tried.

Arnd, maybe you can shed a light on why it is so?

P.S. The workaround is to open code using readq()/writeq() [with
swab64() for BE].

-- 
With Best Regards,
Andy Shevchenko