Re: [PATCH v7] mmc: Add mmc CMD+ACMD passthrough ioctl

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On Tue, 26 Apr 2011, Arnd Bergmann wrote:
> On Friday 22 April 2011, John Calixto wrote:
> > Allows appropriately-privileged applications to send CMD (normal) and
> > ACMD (application-specific; preceded with CMD55) commands to
> > cards/devices on the mmc bus.  This is primarily useful for enabling the
> > security functionality built in to every SD card.
> > 
> > It can also be used as a generic passthrough (e.g. to enable virtual
> > machines to control mmc bus devices directly).  However, this use case
> > has not been tested rigorously.  Generic passthrough testing was only
> > conducted for a few non-security opcodes to prove the feasibility of the
> > passthrough.
> > 
> > Since any opcode can be sent using this passthrough, it is very possible
> > to render the card/device unusable.  Applications that use this ioctl
> > must have CAP_SYS_RAWIO.
> > 
> > Security commands tested on TI PCIxx12 (SDHCI), Sigma Designs SMP8652
> > SoC, TI OMAP3621 SoC, TI OMAP3630 SoC, Samsung S5PC110 SoC, Qualcomm
> > MSM7200A SoC.
> > 
> > Signed-off-by: John Calixto <john.calixto@xxxxxxxxxxxxxx>
> > Reviewed-by: Andrei Warkentin <andreiw@xxxxxxxxxxxx>
> 
> The implementation looks good to me now,
> 
> Reviewed-by: Arnd Bergmann <arnd@xxxxxxxx>
> 
> I'll leave the final decision whether this is a good feature to have
> to Chris. I still believe that we should have per-command ioctls
> for the security feature, but getting there would require someone
> to implement it, and I'm not going to do that.
> 


Arnd - Thanks a lot for the review and your help getting the
implementation right!

Chris - What do you think?  How should I proceed here?

John
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