netdev - Re: [PATCH net-next v7 1/8] bnxt_en: Add auxiliary driver support

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Date:   Tue, 17 Jan 2023 22:32:18 -0800
From:   Ajit Khaparde <ajit.khaparde@...adcom.com>
To:     Leon Romanovsky <leonro@...dia.com>
Cc:     Jakub Kicinski <kuba@...nel.org>, andrew.gospodarek@...adcom.com,
        davem@...emloft.net, edumazet@...gle.com, jgg@...pe.ca,
        linux-kernel@...r.kernel.org, linux-rdma@...r.kernel.org,
        michael.chan@...adcom.com, netdev@...r.kernel.org,
        pabeni@...hat.com, selvin.xavier@...adcom.com
Subject: Re: [PATCH net-next v7 1/8] bnxt_en: Add auxiliary driver support

On Tue, Jan 17, 2023 at 4:31 AM Leon Romanovsky <leonro@...dia.com> wrote:
>
> On Mon, Jan 16, 2023 at 08:56:25PM -0800, Jakub Kicinski wrote:
> > On Sat, 14 Jan 2023 12:39:09 -0800 Ajit Khaparde wrote:
> > > > > +static void bnxt_aux_dev_release(struct device *dev)
> > > > > +{
> > > > > +     struct bnxt_aux_dev *bnxt_adev =
> > > > > +             container_of(dev, struct bnxt_aux_dev, aux_dev.dev);
> > > > > +     struct bnxt *bp = netdev_priv(bnxt_adev->edev->net);
> > > > > +
> > > > > +     bnxt_adev->edev->en_ops = NULL;
> > > > > +     kfree(bnxt_adev->edev);
> > > >
> > > > And yet the reference counted "release" function accesses the bp->adev
> > > > like it must exist.
> > > >
> > > > This seems odd to me - why do we need refcounting on devices at all
> > > > if we can free them synchronously? To be clear - I'm not sure this is
> > > > wrong, just seems odd.
> > > I followed the existing implementations in that regard. Thanks
> >
> > Leon, could you take a look? Is there no problem in assuming bnxt_adev
> > is still around in the release function?
>
> You caught a real bug. The auxdev idea is very simple - it needs to
> behave like driver core, but in the driver itself.
>
> As such, bnxt_aux_dev_free() shouldn't be called after bnxt_rdma_aux_device_uninit().
> Device will be released through auxiliary_device_uninit();
Ok. But..
bnxt_aux_dev_free() is actually freeing up the private memory allocated
for holding the pointer returned by my_aux_dev_alloc(xxx);
The aux device is freed via the auxiliary_device_uninit only.

>
> BTW, line 325 from below shouldn't exist too.
ACK

>
>   312 void bnxt_rdma_aux_device_uninit(struct bnxt *bp)
>   313 {
> ...
>   325         if (bnxt_adev->id >= 0)
>   326                 ida_free(&bnxt_aux_dev_ids, bnxt_adev->id);
>
> And one line bnxt_aux_dev_alloc() needs to be deleted too.
To avoid confusion, I will refactor and rename the code handling
auxiliary_device alloc, cleanup and the alloc, cleanup of priv
pointers used for bookkeeping.

I hope the new patchset will address the concerns raised.

>
> Thanks

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