Re: [PATCH] libata: Integrate ACPI-based PATA/SATA hotplug - version 2

[Jeff Garzik <jeff@garzik.org>]

Matthew Garrett wrote:
> Modern laptops with hotswap bays still tend to utilise a PATA interface 
> on a SATA bridge, generally with the host controller in some legacy 
> emulation mode rather than AHCI. This means that the existing hotplug 
> code in libata is unable to work. The ACPI specification states that 
> these devices can send notifications when hotswapped, which avoids the 
> need to obtain notification from the controller. This patch uses the 
> existing libata-acpi code and simply registers a notification in order 
> to trigger a rescan whenever the firmware signals an event.
> 
> Signed-off-by: Matthew Garrett <mjg59@srcf.ucam.org>
> 
> ---
> 
> Testing on an HP with the hotplug device as the slave on a PATA channel 
> flagged a bug - the notification needs to be tied to the channel handle 
> as well as the device ones. With this version, I can happily hotswap the 
> HP device. It ends up sitting for a few seconds while failing to 
> revalidate, but then recovers with everything working fine.

the code looks correct.  I have one main reservation.

how can we be sure that this is active only where other hand-programmed 
hotplug code is absent?

ACPI doesn't inherently know which of our controllers are already set up 
to do hotplug, so it seems like there is a possibility of conflict if 
both the firmware and the controller are chirping.

If we can quell my fears in that area, I'm ok with the change.

	Jeff