Re: [PATCH RFC 1/3] tpm_crb: expand struct crb_control_area to struct crb_regs

From: Jarkko Sakkinen
Date: Sun Oct 09 2016 - 14:09:21 EST


On Sun, Oct 09, 2016 at 10:49:05AM -0600, Jason Gunthorpe wrote:
> On Sun, Oct 09, 2016 at 12:38:18PM +0300, Jarkko Sakkinen wrote:
> > On Sat, Oct 08, 2016 at 07:42:56PM -0600, Jason Gunthorpe wrote:
> > > On Sun, Oct 09, 2016 at 03:15:09AM +0300, Jarkko Sakkinen wrote:
> > > > + ctrl = crb_map_res(dev, priv, &io_res, buf->control_address,
> > > > + sizeof(struct crb_regs) -
> > > > + offsetof(struct crb_regs, ctrl_req));
> > > > + if (IS_ERR(ctrl))
> > > > + return PTR_ERR(ctrl);
> > > > +
> > > > + /* The control area always overrlaps IO memory mapped from the ACPI
> > > > + * object with CRB start only devices. Thus, this is perfectly safe.
> > > > + */
> > > > + priv->regs = (void *)((unsigned long)ctrl -
> > > > + offsetof(struct crb_regs, ctrl_req));
> > >
> > > Hum. No, this makes bad assumptions about the structure of iomapping.
> > >
> > > The map itself needs to be done with the adjustment:
> > >
> > > ctrl = crb_map_res(dev, priv, &io_res, buf->control_address -
> > > offsetof(struct crb_regs, ctrl_req),
> > > sizeof(struct crb_regs));
> >
> > That would be wrong address for the control area as it does not start
> > from the beginning of CRB registers.
>
> Of course, I just pointed out what the map call should look like
>
> Something like this
>
> priv->regs = crb_map_res(dev, priv, &io_res, buf->control_address -
> offsetof(struct crb_regs, ctrl_req),
> sizeof(struct crb_regs));
> ctrl = &priv->regs.ctrl_req;
>
> > I think the crb_map_io and crb_map_res are too generic. Better way to do
> > things would be to validate that assumptions for these two cases hold.
>
> If the driver is going to be using a negative offset like this, then
> it very much should validate the assumptions before doing it.
>
> and not even map these regsiters if they are not supported by
> hardware.

Yes, that's what the point I tried to make in my response in the part
that is not quoted here.

/Jarkko