linux-kernel - Re: [PATCH v4 1/6] driver core: Fix driver_deferred_probe_check

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Message-ID: <20200220155503.GD955802@ripper>
Date:   Thu, 20 Feb 2020 07:55:03 -0800
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     John Stultz <john.stultz@...aro.org>
Cc:     lkml <linux-kernel@...r.kernel.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>,
        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: Re: [PATCH v4 1/6] driver core: Fix
 driver_deferred_probe_check_state() logic

On Wed 19 Feb 21:04 PST 2020, John Stultz wrote:

> 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@...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: 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>
> Change-Id: I8349b7a403ce8cbce485ea0a0a5512fddffb635c

Please drop the Change-Id.

> ---
> 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

As pointed out by Rafael, this should be Return:

With that addressed, you have my
Reviewed-by: Bjorn Andersson <bjorn.andersson@...aro.org>

Regards,
Bjorn

> + * 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
>