On Fri, Jan 23, 2015 at 12:09 AM, Rafael J. Wysocki <rjw@xxxxxxxxxxxxx> wrote: > On Thursday, January 22, 2015 12:13:13 PM Octavian Purdila wrote: >> On Thu, Jan 22, 2015 at 4:00 AM, Rafael J. Wysocki <rjw@xxxxxxxxxxxxx> wrote: <snip> >> The idea here is to set the companion for the MFD sub-devices. Mika's >> commit "mfd: Add ACPI support" propagates the parent's companion to >> the MFD sub-devices, so it is sufficient to set the ACPI companion to >> the USB device. > > For the USB device itself you'll then end up with an incomplete binding (you > can't get back to the USB device from the ACPI object), so no, it isn't > sufficient. > >> Then, the companion will be propagated to the sub-devices after which >> acpi_bind_one() will be called for the sub-devices from >> mfd_add_devices (via platform_device_add -> device_add -> >> platform_notify). > > In fact, your use case doesn't seem to cover any of the use cases that > the Mika's commit addressed. Namely, your parent device doesn't have > an ACPI companion to start with and you want your MFD cells to be bound > to the "DLN2000" thing. That's why you're setting the ACPI companion > for the USB device, isn't it? > >> It is true that the USB dev will have its ACPI companion set without >> having acpi_bind_one called but I do not see any harm in that. Even >> though acpi_unbind_one() is called it will not find the USB dev on the >> physical node list so no put_device() imbalance is caused. > > Well, there are places where it matters. Some links in sysfs will be missing > for one example. Also please see the changelog of commit 52870786ff5d (ACPI: > Use ACPI companion to match only the first physical device). > > Bottom line: You really should be using acpi_bind_one() here and > acpi_unbind_one() on disconnect if you have to. > OK, I understand now. >> > And no, "Let's come up with a patch that sort of works, throw it at the maintainers >> > and see what happens" is not an acceptable approach, sorry. >> >> This patch is based on your feedback of the previous RFC patch set: > > Oh, is it? I can't recall advising you to use request_firmware() for > uploading ACPI tables or some other questionable things that the patch is > doing. > > And if it still was an RFC, that wouldn't be a problem, but if you just send > non-RFC patches out, that means you want people to merge them. This is bad > if the patches in question are not in a good enough shape and this one isn't. > Yes, this should have been tagged with RFC, sorry about that. > Now, why is this a bad idea to load ACPI tables from a driver using > request_firmware()? Because those tables are not device firmare. They are > not firmware that you load into a device to make it work (which then works > with all instances of the given hardware), they are part of system configuration > information and have to match what's there in the system. For instance, if you > ship your example SSDT with a general-purpose distro, it may just not match the > hardware configuration of systems that people will try to use it with. > > So, while it is sort of OK to look up "DLN2000" and bind the USB device to > that by hand (although this looks ugly to me), it is not OK to load a random > custom SSDT if it is missing. > > We need to add a generic mechanism for loading custom SSDTs not present in the > firmware image and maybe even to load them on demand, but that cannot happen in > an ad-hoc way. So the entire table loading-unloading code in your patch can go > away for now and you need to fail probing if the "DLN2000" ACPI object is not > present. > That sounds interesting, I like the idea of a generic mechanism for loading custom SSDTs. Do you have any initial thoughts/pointers for starting that? Thanks for the review and feedback. -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
