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From:   Patrick Venture <venture@google.com>
Date:   Wed, 27 Mar 2019 12:50:50 -0700
Message-ID: <CAO=notwnVoj1KdqBsWU-XXz0jBy990GP4eOVuUStJh8EmpvTQg@mail.gmail.com>
Subject: Re: [PATCH v7 2/2] drivers/misc: Add Aspeed P2A control driver
To:     Greg KH <gregkh@linuxfoundation.org>
Cc:     Arnd Bergmann <arnd@arndb.de>, Joel Stanley <joel@jms.id.au>,
        Andrew Jeffery <andrew@aj.id.au>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@lists.infradead.org>,
        linux-aspeed@lists.ozlabs.org
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On Wed, Mar 27, 2019 at 12:01 PM Patrick Venture <venture@google.com> wrote:
>
> On Wed, Mar 27, 2019 at 11:54 AM Greg KH <gregkh@linuxfoundation.org> wrote:
> >
> > On Wed, Mar 27, 2019 at 11:44:36AM -0700, Patrick Venture wrote:
> > > On Wed, Mar 27, 2019 at 11:28 AM Greg KH <gregkh@linuxfoundation.org> wrote:
> > > >
> > > > On Tue, Mar 12, 2019 at 09:31:01AM -0700, Patrick Venture wrote:
> > > > > +     phys_addr_t mem_base;
> > > >
> > > > Is this really a 32bit value?
> > >
> > > It's going to be a 32-bit value if this is in the dts for one of the
> > > correspondingly supported aspeed models.
> > >
> > > >
> > > > Your ioctl thinks it is:
> > > >
> > > > > +struct aspeed_p2a_ctrl_mapping {
> > > > > +     __u32 addr;
> > > >
> > > > Does this driver not work on a 64bit kernel?
> > >
> > > This driver is aimed at only 32-bit hardware (ast2400/2500).  I
> > > modeled the approach after the aspeed-lpc-ctrl driver as it's
> > > providing similar functionality.
> > >
> > > >
> > > > > +     __u32 length;
> > > > > +     __u32 flags;
> > > > > +};
> > > >
> > > > addr really should be __u32 here so you don't have to mess with 32/64
> > > > bit user/kernel issues, right?
> > >
> > > Add is __u32 there.  Are you suggesting it shouldn't be?
> >
> > Ugh, yes, sorry, I meant to say "__u64".
> >
> > If you all insist that this is all that is ever going to be needed, ok,
> > but I reserve the right to complain in 4 years when this needs to be
> > changed :)
>
> In the event the ast2600 comes out and is 64-bit -- I can't imagine
> that's likely to happen.  I can take solace that this won't be the
> only thing that needs retrofitting.  But it wouldn't kill me to just
> make the change.  I'll just have to tweak it to return failure in the
> event the address provided isn't found in any region...
>
> Is that all that needs to change for 64-bit addressing support - given
> your read of the driver?

I should have v8 for review shortly.

>
> >
> > thanks,
> >
> > greg k-h