Re: [PATCH v7 3/4] driver core: shut down devices asynchronously

stuart hayes
2024-07-02T19:00:15Z

On 7/2/2024 12:04 AM, Christoph Hellwig wrote:
> On Mon, Jul 01, 2024 at 12:57:40PM -0500, stuart hayes wrote:
>>> We discussed this before, but there is no summary of it and I of course
>>> forgot the conclusion:
>>>
>>> - why don't we do this by default?
>>
>> It is done by default in this version, for devices whose drivers opt-in.
>>
>> In the previous discussion, you mentioned that you thought "safe" was the
>> only sensible option (where "safe" was driver opt-in to async shutdown)...
>> that is the default (and only) option with this version. Greg K-H also
>> requested opt-in as well, and suggested that "on" (driver opt-out) could
>> be removed.
>>
>>> - why is it safe to user enable it?
>>
>> I guess it isn't necessarily safe, if there are any drivers that can't
>> handle their devices shutting down asynchronously. I thought it would be
>> nice to be able to enable driver opt-in from user space for testing, before
>> changing the default setting for the driver.
>
> I was mostly getting into the contradiction that either we think the
> async shutdown is safe everywhere, in which case we don't need a driver
> opt-in, or it is not, in which case allowing user to just enabled it
> also seems like a bad idea.
>

I understand. My thinking was that is was very likely to be safe (the initial
version of this patch didn't have an opt-in or opt-out).

I have no issue removing the sysfs attribute if you think that's best.

>> I can correct these lines. I thought that an 80 character line length limit
>> was no longer required, and saw another line a few lines above these that was
>> even longer... and the checkpatch script didn't flag it either.
>
> checkpatch is unfortunately completely broken, it flags totally harmless
> things and doesn't catch other things. > 80 characters are allowed for
> individual lines where it improves readability. The exact definition
> of that depends on the maintainers and reviewers, but outside of
> string constants I can't really find anything where it does.

Got it, thanks for the feedback.