linux-kernel - [PATCH v5 1/6] driver core: Fix driver_deferred_probe_check

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Date:   Tue, 25 Feb 2020 05:08:23 +0000
From:   John Stultz <john.stultz@...aro.org>
To:     lkml <linux-kernel@...r.kernel.org>
Cc:     John Stultz <john.stultz@...aro.org>,
        Rob Herring <robh@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Kevin Hilman <khilman@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Pavel Machek <pavel@....cz>, Len Brown <len.brown@...el.com>,
        Todd Kjos <tkjos@...gle.com>,
        Saravana Kannan <saravanak@...gle.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Thierry Reding <treding@...dia.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-pm@...r.kernel.org
Subject: [PATCH v5 1/6] driver core: Fix driver_deferred_probe_check_state() logic

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 late_initcall has passed, and modules are not enabled
  it returns -ENODEV

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

* In all other cases, it returns -EPROBE_DEFER

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@...nel.org>
Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc: Kevin Hilman <khilman@...nel.org>
Cc: Ulf Hansson <ulf.hansson@...aro.org>
Cc: Pavel Machek <pavel@....cz>
Cc: Len Brown <len.brown@...el.com>
Cc: Todd Kjos <tkjos@...gle.com>
Cc: Saravana Kannan <saravanak@...gle.com>
Cc: Bjorn Andersson <bjorn.andersson@...aro.org>
Cc: Liam Girdwood <lgirdwood@...il.com>
Cc: Mark Brown <broonie@...nel.org>
Cc: Thierry Reding <treding@...dia.com>
Cc: Linus Walleij <linus.walleij@...aro.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: linux-pm@...r.kernel.org
Signed-off-by: John Stultz <john.stultz@...aro.org>
---
v4:
* Simplified logic suggested by Andy Shevchenko
* Clarified commit message to focus on logic change
v5:
* Cleanup comment wording as suggested by Rafael
* Tweaked the logic to use Saravana's suggested conditionals
---
 drivers/base/dd.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index b25bcab2a26b..d75b34de6964 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -237,24 +237,26 @@ __setup("deferred_probe_timeout=", deferred_probe_timeout_setup);
 
 static int __driver_deferred_probe_check_state(struct device *dev)
 {
-	if (!initcalls_done)
-		return -EPROBE_DEFER;
+	if (!IS_ENABLED(CONFIG_MODULES) && initcalls_done)
+		return -ENODEV;
 
 	if (!deferred_probe_timeout) {
 		dev_WARN(dev, "deferred probe timeout, ignoring dependency");
 		return -ETIMEDOUT;
 	}
 
-	return 0;
+	return -EPROBE_DEFER;
 }
 
 /**
  * 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.
+ * Return:
+ * -ENODEV if initcalls have completed and modules are disabled.
+ * -ETIMEDOUT if the deferred probe timeout was set and has expired
+ *  and modules are enabled.
+ * -EPROBE_DEFER in other cases.
  *
  * Drivers or subsystems can opt-in to calling this function instead of directly
  * returning -EPROBE_DEFER.
@@ -264,7 +266,7 @@ int driver_deferred_probe_check_state(struct device *dev)
 	int ret;
 
 	ret = __driver_deferred_probe_check_state(dev);
-	if (ret < 0)
+	if (ret != -ENODEV)
 		return ret;
 
 	dev_warn(dev, "ignoring dependency for device, assuming no driver");
@@ -292,7 +294,7 @@ int driver_deferred_probe_check_state_continue(struct device *dev)
 	int ret;
 
 	ret = __driver_deferred_probe_check_state(dev);
-	if (ret < 0)
+	if (ret != -ENODEV)
 		return ret;
 
 	return -EPROBE_DEFER;
-- 
2.17.1