[PATCH] mmc: mmci.c: Defer probe() in case of missing GPIOs

On Sat, Jun 16, 2012 at 04:57:48PM +0200, Roland Stigge wrote:

On 16/06/12 16:26, Russell King - ARM Linux wrote:

quoted

On Sat, Jun 16, 2012 at 04:14:59PM +0200, Roland Stigge wrote:

quoted

If the GPIOs used by the MMCI driver are not registered yet when the
driver is probe()d, they can't be used. This happens if the mmci driver
is probed before the respective GPIO controller (e.g. on the LPC32xx
EA3250 board, the PCA9532 GPIO controller would be initialized via DT
after mmci). Therefore, we defer mmci in this case.

This code is wrong.  There are platforms where plat->gpio_cd is negative
(because there isn't an associated GPIO) and we still expect the driver
to successfully bind.  In that case, the driver gets the CD and WP
information via the status callback.

So this is an incompatible change with existing (and required) driver
behaviour.

As someone just told me, in the case of no GPIO, we would have gpio_cd
== -ENODEV. Would it be sufficient to check for -ENODEV (in which case
we would do without GPIO), and otherwise return -EPROBE_DEFER?

Sigh.  New rules which jump up when no one's read the bloody code.
That's intensely frustrating.

Why can't the *new* DT parsing code set the GPIOs to -EPROBE_DEFER when
*it* wants them to mean "we should defer" ?  Why should the DT code
have sole use over "-1" ?  That would be *far* more logical and wouldn't
clash with anything in existing use.