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Subject[PATCH v5 1/6] driver core: Fix driver_deferred_probe_check_state() logic
Date
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@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: Saravana Kannan <saravanak@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>
---
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
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