Messages in this thread | | | From | Saravana Kannan <> | Date | Tue, 30 Aug 2022 10:34:31 -0700 | Subject | Re: [PATCH v2] ARM: Add sanity check for dev->periphid in amba_probe() |
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On Tue, Aug 30, 2022 at 3:36 AM Russell King (Oracle) <linux@armlinux.org.uk> wrote: > > On Tue, Aug 30, 2022 at 06:31:14PM +0800, Leizhen (ThunderTown) wrote: > > On 2022/8/30 18:07, Russell King (Oracle) wrote: > > > For an amba driver, drv->bus will always be pointing at amba_bustype. > > > That always has a "match" operation. Therefore, the default of '1' > > > above will *never* be used for an AMBA driver. > > > > > > If drv->bus does not point at amba_bustype, then amba_probe() will > > > not be called for "drv". > > > > > > Therefore, amba_match() must always be called before amba_probe(). > > > > Oh, I was careless. I think it's drv->match. But the processing flow > > will continue to go to "dev->bus->probe". > > > > __driver_attach(): > > ret = driver_match_device(drv, dev); > > if (ret == 0) { > > /* no match */ > > return 0; > > } else if (ret == -EPROBE_DEFER) { <------no return in this branch > > dev_dbg(dev, "Device match requests probe deferral\n"); > > dev->can_match = true; > > driver_deferred_probe_add(dev); > > } else if (ret < 0) { > > dev_dbg(dev, "Bus failed to match device: %d\n", ret); > > return ret; > > } /* ret > 0 means positive match */ > > > > ... ... > > driver_probe_device(drv, dev); > > ...... > > dev->bus->probe > > And that makes no sense, is an already known issue, and there is a patch > to fix it: > > https://lore.kernel.org/all/20220817184026.3468620-1-isaacmanjarres@google.com/
Russell,
Thanks for discussing this further and pointing out the other fix. I assumed Leizhen was talking about an instance of device_driver_attach() which allows probe to be called without match. Thankfully that function is used only by some specific frameworks/buses types. I did a cursory check and I don't see any intersection with we amba.
-Saravana P.S: I hate that function exists, as it just throws a wrench in the whole driver core design and adds corner cases to a lot of generic driver core design.
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