Re: [PATCH v7 4/9] driver: core: allow modifying device_links flags

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On Fri, 2024-01-26 at 09:13 +0100, Nuno Sá wrote:
> On Thu, 2024-01-25 at 16:50 -0800, Saravana Kannan wrote:
> > On Thu, Jan 25, 2024 at 12:11 AM Nuno Sá <noname.nuno@xxxxxxxxx> wrote:
> > > 
> > > 
> > > Hi Saravana,
> > > 
> > > Thanks for your feedback,
> > > 
> > > On Wed, 2024-01-24 at 19:21 -0800, Saravana Kannan wrote:
> > > > On Tue, Jan 23, 2024 at 7:14 AM Nuno Sa via B4 Relay
> > > > <devnull+nuno.sa.analog.com@xxxxxxxxxx> wrote:
> > > > > 
> > > > > From: Nuno Sa <nuno.sa@xxxxxxxxxx>
> > > > > 
> > > > > If a device_link is previously created (eg: via
> > > > > fw_devlink_create_devlink()) before the supplier + consumer are both
> > > > > present and bound to their respective drivers, there's no way to set
> > > > > DL_FLAG_AUTOREMOVE_CONSUMER anymore while one can still set
> > > > > DL_FLAG_AUTOREMOVE_SUPPLIER. Hence, rework the flags checks to allow
> > > > > for DL_FLAG_AUTOREMOVE_CONSUMER in the same way
> > > > > DL_FLAG_AUTOREMOVE_SUPPLIER is done.
> > > > 
> > > > Curious, why do you want to set DL_FLAG_AUTOREMOVE_CONSUMER?
> > > > Especially if fw_devlink already created the link? You are effectively
> > > > trying to delete the link fw_devlink created if any of your devices
> > > > unbind.
> > > > 
> > > 
> > > Well, this is still useful in the modules case as the link will be relaxed
> > > after
> > > all devices are initialized and that will already clear AUTOPROBE_CONSUMER
> > > AFAIU. But, more importantly, if I'm not missing anything, in [1],
> > > fw_devlinks
> > > will be dropped after the consumer + supplier are bound which means I
> > > definitely
> > > want to create a link between my consumer and supplier.
> > > 
> > > FWIW, I was misunderstanding things since I thought
> > > DL_FLAG_AUTOREMOVE_CONSUMER
> > > was needed to make sure the consumer is unbound before the supplier. But
> > > for
> > > that I think I can even pass 0 in the flags as I only need the link to be
> > > MANAGED. Still, I think having DL_FLAG_AUTOREMOVE_CONSUMER makes sense.
> > 
> > As you noticed, your understanding of DL_FLAG_AUTOREMOVE_CONSUMER is
> > not correct. There's almost never a good reason to drop a device link.
> > Even when a device/driver are unbound, we still want future probe
> > attempts to make use of the dependency info and block a device from
> > probing if the supplier hasn't probed.
> > 
> 
> Yeah that makes sense and is making me thinking that I should change my call
> (in
> patch 7 to use the MANAGED flag instead of AUTOREMOVE_CONSUMER). Sure,
> AUTOREMOVE_CONSUMER won't matter most cases but if someone disables
> fw_devlinks
> then it matters.
> 

Yeah, just realized MANAGED is not a valid flag one can pass to
device_link_add() :)

- Nuno Sá
> 






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