[resend/standalone PATCH v4] Add auxiliary bus support

[Parav Pandit]

> From: Leon Romanovsky <leonro at nvidia.com>
> Sent: Friday, December 4, 2020 6:02 PM
> 
> On Fri, Dec 04, 2020 at 12:42:46PM +0100, Greg KH wrote:
> > On Wed, Dec 02, 2020 at 04:54:24PM -0800, Dan Williams wrote:
> > > From: Dave Ertman <david.m.ertman at intel.com>
> > >
> > > Add support for the Auxiliary Bus, auxiliary_device and auxiliary_driver.
> > > It enables drivers to create an auxiliary_device and bind an
> > > auxiliary_driver to it.
> > >
> > > The bus supports probe/remove shutdown and suspend/resume
> callbacks.
> > > Each auxiliary_device has a unique string based id; driver binds to
> > > an auxiliary_device based on this id through the bus.
> > >
> > > Co-developed-by: Kiran Patil <kiran.patil at intel.com>
> > > Co-developed-by: Ranjani Sridharan
> > > <ranjani.sridharan at linux.intel.com>
> > > Co-developed-by: Fred Oh <fred.oh at linux.intel.com>
> > > Co-developed-by: Leon Romanovsky <leonro at nvidia.com>
> > > Signed-off-by: Kiran Patil <kiran.patil at intel.com>
> > > Signed-off-by: Ranjani Sridharan <ranjani.sridharan at linux.intel.com>
> > > Signed-off-by: Fred Oh <fred.oh at linux.intel.com>
> > > Signed-off-by: Leon Romanovsky <leonro at nvidia.com>
> > > Signed-off-by: Dave Ertman <david.m.ertman at intel.com>
> > > Reviewed-by: Pierre-Louis Bossart
> > > <pierre-louis.bossart at linux.intel.com>
> > > Reviewed-by: Shiraz Saleem <shiraz.saleem at intel.com>
> > > Reviewed-by: Parav Pandit <parav at mellanox.com>
> > > Reviewed-by: Dan Williams <dan.j.williams at intel.com>
> > > Reviewed-by: Martin Habets <mhabets at solarflare.com>
> > > Link:
> > > https://lore.kernel.org/r/20201113161859.1775473-2-david.m.ertman@in
> > > tel.com
> > > Signed-off-by: Dan Williams <dan.j.williams at intel.com>
> > > ---
> > > This patch is "To:" the maintainers that have a pending backlog of
> > > driver updates dependent on this facility, and "Cc:" Greg. Greg, I
> > > understand you have asked for more time to fully review this and
> > > apply it to driver-core.git, likely for v5.12, but please consider
> > > Acking it for v5.11 instead. It looks good to me and several other
> stakeholders.
> > > Namely, stakeholders that have pressure building up behind this
> > > facility in particular Mellanox RDMA, but also SOF, Intel Ethernet,
> > > and later on Compute Express Link.
> > >
> > > I will take the blame for the 2 months of silence that made this
> > > awkward to take through driver-core.git, but at the same time I do
> > > not want to see that communication mistake inconvenience other
> > > parties that reasonably thought this was shaping up to land in v5.11.
> > >
> > > I am willing to host this version at:
> > >
> > > git://git.kernel.org/pub/scm/linux/kernel/git/djbw/linux
> > > tags/auxiliary-bus-for-5.11
> > >
> > > ...for all the independent drivers to have a common commit baseline.
> > > It is not there yet pending Greg's Ack.
> > >
> > > For example implementations incorporating this patch, see Dave
> > > Ertman's SOF series:
> > >
> > > https://lore.kernel.org/r/20201113161859.1775473-2-david.m.ertman@in
> > > tel.com
> > >
> > > ...and Leon's mlx5 series:
> > >
> > > http://lore.kernel.org/r/20201026111849.1035786-1-leon@kernel.org
> > >
> > > PS: Greg I know I promised some review on newcomer patches to help
> > > with your queue, unfortunately Intel-internal review is keeping my
> > > plate full. Again, I do not want other stakeholder to be waiting on
> > > me to resolve that backlog.
> >
> > Ok, I spent some hours today playing around with this.  I wrote up a
> > small test-patch for this (how did anyone test this thing???).
> 
> We are running all verifications tests that we have over our
> mlx5 driver. It includes devices reloads, power failures, FW reconfiguration to
> emulate different devices with and without error injections and many more.
> Up till now, no new bugs that are not known to us were found.
> 
Subfunction patchset [1] that is using auxiliary bus in mlx5 driver is also been used by verification and performance tests.

[1] https://lore.kernel.org/linux-rdma/20201112192424.2742-1-parav@nvidia.com/