Re: [RFC PATCH 0/4] device_schedule_reprobe(): core helper and conversions

[Luiz Augusto von Dentz]

Hi Hans,

On Tue, Aug 11, 2026 at 4:51 AM Hans de Goede
<johannes.goede@xxxxxxxxxxxxxxxx> wrote:
>
> Hi,
>
> On 11-Aug-26 10:07, Greg Kroah-Hartman wrote:
> > On Tue, Aug 11, 2026 at 09:32:45AM +0200, Hans de Goede wrote:
> >> Hi Greg,
> >>
> >> On 11-Aug-26 04:33, Greg Kroah-Hartman wrote:
> >>> On Tue, Aug 11, 2026 at 01:47:17AM +0100, Daniel Golle wrote:
> >>>> Three in-tree drivers (iwlwifi, hci_h5, btintel_pcie) schedule a
> >>>> deferred re-probe of their own device from a work item in module
> >>>> text.
> >>>
> >>> That's a mess, why?  Why not fix that up to not do that?  Thousands of
> >>> other kernel drivers do not do that, what makes these so special?
> >>
> >> I can only speak for the hci_h5 driver where I added the reprobe code-path.
> >>
> >> The problem is some of the Bluetooth HCI devices using hci_h5 loose all
> >> state during system-suspend. This means that the HCI and the Bluetooth core
> >> end up being out of sync.
> >>
> >> So we basically need to tear down and re-build everything including
> >> e.g. the firmware upload which happens at probe(). Doing a full reprobe
> >> is by far the easiest way to do this.
> >>
> >> I suspect the other 4 users + the pending driver which triggered
> >> this are similar.
> >
> > Full reprobe feels different than the THIS_MODULE stuff, which is what I
> > objected to here.
>
> Right, the helper from 1/4 to safely do reprobe from a worker actually
> removes the need for THIS_MODULE stuff :)
>
> The THIS_MODULE stuff in the open-coded implementations is there to
> avoid someone doing a rmmod while the reprobe is running. The new
> helper replaces this with some checks in the workqueue function
> checking the driver has not been rmmod-ed in the mean time.
>
> >> Sure we can do the whole tear-down + setup from some worker
> >> scheduled at resume, while keep the driver attached but if we need
> >> to duplicate that over 4 drivers + the pending driver which triggers
> >> this then IMHO those 5 users are a pattern which deserves having
> >> some helper to do this through the existing probe() + remove(),
> >> rather then requiring those 5 drivers to open code this themselves.
> >>
> >> Note that we already have device_reprobe(), which has 15 existing
> >> users. This series just adds a helper to do a device_reprobe() from
> >> a worker in a safe way.
> >
> > That feels a bit better, as long as this code really is "safe" :)
> >
> > So, how can this be tested and fixed up so it isn't a RFC anymore?
>
> To me it looks like the main things are:
>
> 1. Agree that a helper to safely do a device_reprobe() from a worker
> is helpful (I think this is done now?)
>
> 2. Get patch 1/4 reviewed. I can do an initial review but I'm not very
> familiar with the driver/device core internals.
>
> 3. Test this. I can test this on a hci_h5 BT HCI that will hit this
> code path.
>
> I'll try to get 2. and 3. done soon-ish.

The 2 Intel drivers are related; they are part of a combo Wi-Fi + BT
solution. This is why they attempt to reprobe each other to recover if
the entire system (not just wifi or bt) has run into a fault and needs
to be recovered as a whole.

As for introducing device_schedule_reprobe that seem to be a great
initiative, thanks for leading it.

-- 
Luiz Augusto von Dentz