On Fri, Dec 4, 2020 at 3:41 AM Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > On Wed, Dec 02, 2020 at 04:54:24PM -0800, Dan Williams wrote: > > From: Dave Ertman <david.m.ertman@xxxxxxxxx> > > > > 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@xxxxxxxxx> > > Co-developed-by: Ranjani Sridharan <ranjani.sridharan@xxxxxxxxxxxxxxx> > > Co-developed-by: Fred Oh <fred.oh@xxxxxxxxxxxxxxx> > > Co-developed-by: Leon Romanovsky <leonro@xxxxxxxxxx> > > Signed-off-by: Kiran Patil <kiran.patil@xxxxxxxxx> > > Signed-off-by: Ranjani Sridharan <ranjani.sridharan@xxxxxxxxxxxxxxx> > > Signed-off-by: Fred Oh <fred.oh@xxxxxxxxxxxxxxx> > > Signed-off-by: Leon Romanovsky <leonro@xxxxxxxxxx> > > Signed-off-by: Dave Ertman <david.m.ertman@xxxxxxxxx> > > Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@xxxxxxxxxxxxxxx> > > Reviewed-by: Shiraz Saleem <shiraz.saleem@xxxxxxxxx> > > Reviewed-by: Parav Pandit <parav@xxxxxxxxxxxx> > > Reviewed-by: Dan Williams <dan.j.williams@xxxxxxxxx> > > Reviewed-by: Martin Habets <mhabets@xxxxxxxxxxxxxx> > > Link: https://lore.kernel.org/r/20201113161859.1775473-2-david.m.ertman@xxxxxxxxx > > Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx> > > --- > > 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@xxxxxxxxx > > > > ...and Leon's mlx5 series: > > > > http://lore.kernel.org/r/20201026111849.1035786-1-leon@xxxxxxxxxx > > > > 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???) and while > it feels awkward in places, and it feels like there is still way too > much "boilerplate" code that a user has to write and manage, I don't > have the time myself to fix it up right now. > > So I'll go apply this to my tree, and provide a tag for everyone else to > be able to pull from for their different development trees so they can > work on. > > I do have 3 follow-on patches that I will send to the list in response > to this message that I will be applying on top of this patch. They do > some minor code formatting changes, as well as change the return type of > the remove function to make it more future-proof. That last change will > require users of this code to change their implementations, but it will > be obvious what to do as you will get a build warning. > > Note, I'm still not comfortable with a few things here. The > documentation feels odd, and didn't really help me out in writing any > test code, which doesn't seem right. Also the use of strings and '.' as > part of the api feels awkward, and messy, and of course, totally > undocumented. > > But, as the use of '.' is undocumented, that means we can change it in > the future! Because no driver or device name should ever be a user api > reliant thing, if we come up with a better way to do all of this in the > future, that shouldn't be a problem to change existing users over to > this. So this is a warning to everyone, you CAN NOT depend on the sysfs > name of a device or bus name for any tool. If so, your userspace tool > is broken. > > Thanks for everyone in sticking with this, I know it's been a long slog, > hopefully this will help some driver authors move forward with their > crazy complex devices :) To me, the documentation was written, and reviewed, more from the perspective of "why not open code a custom bus instead". So I can see after the fact how that is a bit too much theory and justification and not enough practical application. Before the fact though this was a bold mechanism to propose and it was not clear that everyone was grokking the "why" and the tradeoffs. I also think it was a bit early to identify consistent design patterns across the implementations and codify those. I expect this to evolve convenience macros just like other parts of the driver-core gained over time. Now that it is in though, another pass through the documentation to pull in more examples seems warranted.
