On Wed, Dec 2, 2020 at 8:39 PM Hans de Goede <hdegoede@xxxxxxxxxx> wrote: > > Hi, > > On 12/2/20 2:49 PM, Rafael J. Wysocki wrote: > > On Sat, Nov 21, 2020 at 9:30 PM Hans de Goede <hdegoede@xxxxxxxxxx> wrote: > >> > >> Hi Rafael, > >> > >> A while ago (almost 2 years ago) I discussed an issue with you about > >> some devices, where some of the methods used during device-addition > >> (such as _HID) may rely on OpRegions of other devices: > >> > >> https://www.spinics.net/lists/linux-acpi/msg86303.html > >> > >> An example of this is the Acer Switch 10E SW3-016 model. The _HID method > >> of the ACPI node for the UART attached Bluetooth, reads GPIOs to detect > >> the installed wifi chip and update the _HID for the Bluetooth's ACPI node > >> accordingly. The current ACPI scan code calls _HID before the GPIO > >> controller's OpRegions are available, leading to the wrong _HID being > >> used and Bluetooth not working. > >> > >> Last week I bought a second hand Acer device, not knowing it was this > >> exact model. Since I now have access to affected hardware I decided to > >> take a shot at fixing this. > >> > >> In the discussion you suggested to split the acpi_bus_scan of the root > >> into 2 steps, first scan devices with an empty _DEP, putting other > >> acpi_handle-s on a list of deferred devices and then in step 2 scan the > >> rest. > >> > >> I'm happy to report that, at least on the affected device, this works > >> nicely. While working on this I came up with a less drastic way to > >> deal with this. As you will see in patch 4 of this series, I decided > >> to first add a more KISS method of deciding which devices to defer > >> to the second scan step by matching by HID. This has the disadvantage > >> of not being a generic solution. But it has the advantage of being a > >> solution which does not potentially regress other devices. > >> > >> Then in patch 5 I actually do add the option to defer or not based on > >> _DEP being empty. I've put this behind a kernel commandline option as > >> I'm not sure we should do this everywhere by default. At least no without > >> a lot more testing. > >> > >> Patch 6 fixes an issue with patch 5 which causes battery devices to stop > >> working. > >> > >> And patch 7 adds some extra HIDs to the list of HIDs which should be > >> ignored when checking if the _DEP list is empty from Linux' pov, iow > >> some extra HIDs which Linux does not bind to. > >> > >> Please let me know what you think about this patch-set. I would be happy > >> to see just patches 1-4 merged. > > > > I took patches 1 and 2, because IMO they are generally useful (I > > rewrote the changelogs to avoid mentioning the rest of the series > > though), > > That is fine. Thanks for taking those. > > > but I have some reservations regarding the rest. > > > > First off, I'm not really sure if failing acpi_add_single_object() for > > devices with missing dependencies is a good idea. IIRC there is > > nothing in there that should depend on any opregions supplied by the > > other devices, so it should be safe to allow it to complete. > > Actually acpi_add_single_object() does depend on ACPI methods > which may depend on opregions, that is the whole reason why > this series is necessary. Otherwise we could just delay the > binding of the driver based in dep_unmet which would be easier. > > Here are 2 actual examples of acpi_add_single_object() calling > ACPI methods which may depend on opregions: > > 1. acpi_add_single_object() calls acpi_init_device_object() which > calls acpi_set_pnp_ids() which fills a bunch if fields of > struct acpi_device with info returned by the acpi_get_object_info() > call. > > Specifically it stores the value returned by the _HID method in > the acpi_device_pnp array for the device and that _HID method is > actually the problem in the example device which started this > series. The _HID method of the bluetooth device reads 2 GPIOs > to get a hw-id (0-3) and then translates the hwid to a _HID > string. If the GPIO opregion's handlers have not registered yet > then the reading of the GPIOs is correctly skipped, and hwid > 0 is assumed, which is wrong in this case. > > 2. I've also seen examples where _STA depends on GPIOs in a similar > manner; and acpi_add_single_object() calls acpi_bus_get_power_flags() > which calls acpi_bus_init_power() which calls acpi_device_is_present() > which depends on _STA results. Well, this means that there is a bug in acpi_bus_attach() which shouldn't call acpi_bus_init_power() which has been called already. And it all means that either deferring acpi_add_single_object() is needed and so there need to be 2 passes in acpi_bus_attach() overall, or acpi_add_single_object() needs to avoid calling methods that may depend on supplied opregions. I guess the latter is rather unrealistic, so the only practical choice is the former. However, I still don't think that the extra list of "dependent devices" is needed.
