[PATCH] drm/panfrost: Add PANFROST_BO_NO{READ,WRITE} flags

[Alyssa Rosenzweig]

> > > > > +	/* Executable implies readable */
> > > > > +	if ((args->flags & PANFROST_BO_NOREAD) &&
> > > > > +	    !(args->flags & PANFROST_BO_NOEXEC))
> > > > > +		return -EINVAL;    
> > > > 
> > > > Generally, executable also implies not-writeable. Should we check that?  
> > > 
> > > We were allowing it until now, so doing that would break the backward
> > > compat, unfortunately.  
> > 
> > Not a problem if you only enforce this starting with the appropriate
> > UABI version, but...
> 
> I still don't see how that solves the <old-userspace,new-kernel>
> situation, since old-userspace doesn't know about the new UABI, and
> there's no version field on the CREATE_BO ioctl() to let the kernel
> know about the UABI used by this userspace program. I mean, we could
> add one, or add a new PANFROST_BO_EXTENDED_FLAGS flag to enforce this
> 'noexec implies nowrite' behavior, but is it really simpler than
> explicitly passing the NOWRITE flag when NOEXEC is passed?

For some reason I thought the ABI version was negotiated (it is in
kbase). Don't worry about it.

That commit is

	Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig at collabora.com>