linux-kernel - Re: Alternative approach to solve the deferred probe

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Message-ID: <56282841.3060802@gmail.com>
Date:	Wed, 21 Oct 2015 17:05:21 -0700
From:	Frank Rowand <frowand.list@...il.com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
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Subject: Re: Alternative approach to solve the deferred probe

On 10/21/2015 1:35 PM, Russell King - ARM Linux wrote:
> On Wed, Oct 21, 2015 at 08:36:23AM -0700, Frank Rowand wrote:
>> On 10/21/2015 1:18 AM, Russell King - ARM Linux wrote:
>>> On Tue, Oct 20, 2015 at 08:58:19PM -0700, Frank Rowand wrote:
>>>> On 10/20/2015 8:46 AM, Russell King - ARM Linux wrote:
>>
>> < snip >
>>
>>>>> +
>>>>>  static bool driver_deferred_probe_enable = false;
>>>>> +
>>>>>  /**
>>>>>   * driver_deferred_probe_trigger() - Kick off re-probing deferred devices
>>>>>   *
>>>>> @@ -188,6 +210,13 @@ static int deferred_probe_initcall(void)
>>>>>  	driver_deferred_probe_trigger();
>>>>
>>>> Couldn't you put the "driver_deferred_probe_report = true" here?  And then
>>>> not add another round of probes.
>>>
>>> The idea is not to report anything for drivers that were deferred
>>> during the normal bootup.  The above is part of the normal bootup,
>>> and the deferred activity should not be warned about.
>>
>> The above is currently the last point for probe to succeed or defer
>> (until possibly, as you mentioned, module loading resolves the defer).
>> If a probe defers above, it will defer again below.  The set of defers
>> should be exactly the same above and below.
> 
> Why should it?

My assertion was incorrect.  A probe in the deferral processing can
result in the driver being placed on the new deferred list, then when
a later probe of another deferred driver succeeds, the first driver
will be moved to the active deferred list, and might succeed on
the second probe attempt (or with the current messages would result
in a second set of deferred messages).  So yes, placing
"driver_deferred_probe_report = true" where your patch put it and
running through the deferred probe processing again is correct.

-Frank
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