[PATCH 03/10] soc: fujitsu: hwb: Add IOC_BB_ALLOC ioctl

[Arnd Bergmann]

On Tue, Jan 12, 2021 at 12:02 PM misono.tomohiro at fujitsu.com
<misono.tomohiro at fujitsu.com> wrote:
> > On Fri, Jan 8, 2021 at 11:52 AM Misono Tomohiro
> > <misono.tomohiro at jp.fujitsu.com> wrote:
> >> >
> > I think this could be simplified into a single write_sysreg_s() with the
> > register number calculated based on sync_args->bb, rather than duplicating
> > the same three lines six times.
>
> I think msr/mrs instructions needs register names at compile time so
> it cannot be calculate dynamically. Or am I misunderstood?

You are correct, I didn't realize it was implemented using a string
concatenation macro and that an inline function version would be
tricky.

> > > @@ -164,6 +386,7 @@ static int fujitsu_hwb_dev_open(struct inode *inode, struct file *filp)
> > >  static const struct file_operations fujitsu_hwb_dev_fops = {
> > >         .owner          = THIS_MODULE,
> > >         .open           = fujitsu_hwb_dev_open,
> > > +       .unlocked_ioctl = fujitsu_hwb_dev_ioctl,
> > >  };
> >
> > All drivers with an ioctl interface should work in compat mode as well,
> > so please add a
> >
> >        .compat_ioctl = compat_ptr_ioctl;
>
>
> A64FX does not support 32-bit mode (aarch32 state).
> So I think unlockd_ioctl is enough or is it better to use compat_ioctl anyway?

It's a good point that this is not supported, but I would suggest adding
it anyway out of principle. It's better to always write code in a portable
way even if you do not expect to need the portability.

       Arnd