On Saturday, November 10, 2012 10:14:47 AM Bjorn Helgaas wrote: > On Sat, Nov 10, 2012 at 4:10 AM, Rafael J. Wysocki <rjw@xxxxxxx> wrote: > > On Friday, November 09, 2012 09:53:26 AM Bjorn Helgaas wrote: > >> On Fri, Nov 9, 2012 at 9:43 AM, Grant Likely <grant.likely@xxxxxxxxxxxx> wrote: > >> > On Fri, Nov 9, 2012 at 4:35 PM, Bjorn Helgaas <bhelgaas@xxxxxxxxxx> wrote: > >> >> On Fri, Nov 9, 2012 at 8:45 AM, Grant Likely <grant.likely@xxxxxxxxxxxx> wrote: > >> >>> On Fri, Nov 9, 2012 at 3:11 PM, Bjorn Helgaas <bhelgaas@xxxxxxxxxx> wrote: > >> >>>> [+cc Greg, Peter, Tony since they acked the original patch [1]] > >> >>>> > >> >>>> On Thu, Nov 8, 2012 at 1:04 PM, Mika Westerberg > >> >>>> <mika.westerberg@xxxxxxxxxxxxxxx> wrote: > >> >>>>> On Thu, Nov 08, 2012 at 12:32:25PM -0700, Bjorn Helgaas wrote: > >> >>>>>> Struct device_driver is a generic structure, so it seems strange to > >> >>>>>> have to include non-generic things like of_device_id and now > >> >>>>>> acpi_match_table there. > >> >>>>> > >> >>>>> Yes, but in a sense the DT and ACPI are "generic". So that they are used to > >> >>>>> describe the configuration of a machine. > >> >>>> > >> >>>> What I meant by "generic" was "useful across all architectures." The > >> >>>> new acpi_match_table and acpi_handle fields [1] are not generic in > >> >>>> that sense because they're present on all architectures but used only > >> >>>> on x86 and ia64. The existing of_match_table and of_node are > >> >>>> similarly unused on many architectures. This doesn't seem like a > >> >>>> scalable strategy to me. Are we going to add a pnpbios_node for x86 > >> >>>> PNPBIOS machines without ACPI, a pdc_hpa for parisc machines with PDC, > >> >>>> etc.? > >> >>>> > >> >>>> [1] https://patchwork.kernel.org/patch/1677221/ > >> >>> > >> >>> Ultimately yes, I think that is what we want to do, > >> >> > >> >> Just to be clear, you think we *should* add things like pnpbios_node, > >> >> pdc_hpa, etc., to struct device, one field for every scheme of telling > >> >> the OS about non-enumerable devices, where only one of the N fields is > >> >> used on any given machine? That seems surprising to me, but maybe I > >> >> just need to be educated :) > >> > > >> > Ah, I see what you're asking. > >> > > >> > In the short term, yes but only because we don't have any other > >> > alternative. What I'd really rather have is a safe way to attach datum > >> > (ie. acpi_device or device_node) to a struct device and get it back > >> > later in a type safe way. > >> > >> Yep, *that* makes perfect sense to me. Something along these lines, maybe: > >> > >> #define dev_is_acpi(d) ((d)->bus == &acpi_bus_type) > > > > No, that's not right. It won't work for things like SPI and I2C with a > > "backing" ACPI device node anyway (and for PCI too, by the way :-)). > > > >> #define dev_acpi_handle(d) (dev_is_acpi(d) ? (acpi_handle) > >> d->datum : NULL) > > > > The problem basically is how we can tell that the given struct device has > > a "backing" object containing device information (e.g. resources) and what > > that "backing" object is. For device trees that would be a struct device_node > > and for ACPI that would be an acpi_handle or a struct acpi_device etc. And by > > the way, they _can_ be used simultaneously, in principle. > > > > So we need something like of_node(dev) or acpi_node(dev), but that can't be > > something following two pointers or calling a function just in order to check > > if the pointer _is_ _there_ in either case. > > > > And since we added of_node to struct device at one point, it is only logical to > > treat ACPI in the same way. If we come up with a better idea _later_, then we > > can convert _all_ things to this new idea, whatever it is. > > > > Are you seriously expecting us to come up with such an idea on the fly just so > > that we can use ACPI support, which already is there in the form of > > archdata.acpi_handle anyway, on equal footing with Device Trees? > > Of course not. I'm just trying to understand where we're headed. > That was not obvious from the patches I've seen so far. No, it wasn't, fair enough. Thanks, Rafael -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
