Re: [PATCH v4] mmc: Add ioctl to let userspace apps send ACMDs

Arnd Bergmann
2011-04-18T14:42:56Z

On Wednesday 13 April 2011, John Calixto wrote:
> > Since the code is limited to ACMD and cannot do arbitrary commands, it's actually
> > not possible to use this for the passthrough scenario, so you should not mention
> > it in the changelog.
> >
> > I would also still advocate something more high-level here because it's limited
> > to a single use case. If you make the ioctl interface do the security commands
> > directly, you would not need to rely on CAP_SYS_RAWIO.
> >
>
> I'm happy to remove the text about passthrough from the changelog, but
> it is a valid use for this ioctl. I agree that ACMD by itself is not
> sufficient for full passthrough, but this patch is a starting point for
> anyone wanting to implement full CMD passthrough.
>
> There are also several ACMD opcodes that are not related to security,
> but to functionality like requesting to change the signalling voltage,
> setting bus width, setting pre-erase block count, etc... I think those
> commands are what caused others to request some kind of capability
> restriction.
>

Ok, I see.

In v6, it seems you have implemented the full CMD passthrough, if I
read it correctly. Is there anything still missing?

Arnd