Re: Bugs in MMC [was: [Bug 10030] Suspend doesn't work when SD cardis inserted]

[Alan Stern]

On Mon, 3 Mar 2008, David Brownell wrote:

> Card insert/remove events can be system wake events though.  Which
> makes that restriction impractical.
> 
> I think hosts need to be able to call mmc_detect_change() as soon as
> they see a stable signal.  The MMC core can hold off handling that
> for a while, if it needs to wait until the code walking the device
> tree gets around to resuming that host.  It's a lot more natural to
> hold off such stuff one time there than in N host drivers; especially
> since the MMC core already has such hold-off code.

That's what ended up happening.  The workqueue used by
mmc_detect_change() was made freezable, so hosts could call the routine
at any time but it wouldn't do anything until the system sleep was
over.

A more flexible approach would avoid freezing the workqueue, and allow 
it to process card removals at any time.  But card insertions would be 
ignored if the mmc_host device was suspended; at resume time the core 
probes for changes that occurred during the sleep.

Alan Stern

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/