[PATCH v4 1/6] driver core: Fix driver_deferred_probe_check_state() logic

[John Stultz <john.stultz@linaro.org>]

driver_deferred_probe_check_state() has some uninituitive behavior.

* From boot to late_initcall, it returns -EPROBE_DEFER

* From late_initcall to the deferred_probe_timeout (if set)
  it returns -ENODEV

* If the deferred_probe_timeout it set, after it fires, it
  returns -ETIMEDOUT

This is a bit confusing, as its useful to have the function
return -EPROBE_DEFER while the timeout is still running. This
behavior has resulted in the somwhat duplicative
driver_deferred_probe_check_state_continue() function being
added.

Thus this patch tries to improve the logic, so that it behaves
as such:

* If deferred_probe_timeout is set, it returns -EPROBE_DEFER
  until the timeout, afterwhich it returns -ETIMEDOUT.

* If deferred_probe_timeout is not set (-1), it returns
  -EPROBE_DEFER until late_initcall, after which it returns

This will make the deferred_probe_timeout value much more
functional, and will allow us to consolidate the
driver_deferred_probe_check_state() and
driver_deferred_probe_check_state_continue() logic in a later
patch.

Cc: Rob Herring <robh@kernel.org>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Kevin Hilman <khilman@kernel.org>
Cc: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Len Brown <len.brown@intel.com>
Cc: Todd Kjos <tkjos@google.com>
Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: Liam Girdwood <lgirdwood@gmail.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Thierry Reding <treding@nvidia.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-pm@vger.kernel.org
Signed-off-by: John Stultz <john.stultz@linaro.org>
Change-Id: I8349b7a403ce8cbce485ea0a0a5512fddffb635c
---
v4:
* Simplified logic suggested by Andy Shevchenko
* Clarified commit message to focus on logic change
---
 drivers/base/dd.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index b25bcab2a26b..bb383dca39c1 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -237,7 +237,7 @@ __setup("deferred_probe_timeout=", deferred_probe_timeout_setup);
 
 static int __driver_deferred_probe_check_state(struct device *dev)
 {
-	if (!initcalls_done)
+	if (!initcalls_done || deferred_probe_timeout > 0)
 		return -EPROBE_DEFER;
 
 	if (!deferred_probe_timeout) {
@@ -252,9 +252,11 @@ static int __driver_deferred_probe_check_state(struct device *dev)
  * driver_deferred_probe_check_state() - Check deferred probe state
  * @dev: device to check
  *
- * Returns -ENODEV if init is done and all built-in drivers have had a chance
- * to probe (i.e. initcalls are done), -ETIMEDOUT if deferred probe debug
- * timeout has expired, or -EPROBE_DEFER if none of those conditions are met.
+ * Returnes -EPROBE_DEFER if initcalls have not completed, or the deferred
+ * probe timeout is set, but not expried.
+ * Returns -ETIMEDOUT if the probe timeout was set and has expired.
+ * Returns -ENODEV if initcalls have completed and the deferred probe timeout
+ * was not set.
  *
  * Drivers or subsystems can opt-in to calling this function instead of directly
  * returning -EPROBE_DEFER.
-- 
2.17.1