On Sat, Nov 10, 2012 at 11:10 AM, Rafael J. Wysocki <r...@sisk.pl> 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.lik...@secretlab.ca> >> wrote: >> > On Fri, Nov 9, 2012 at 4:35 PM, Bjorn Helgaas <bhelg...@google.com> wrote: >> >> On Fri, Nov 9, 2012 at 8:45 AM, Grant Likely <grant.lik...@secretlab.ca> >> >> wrote: >> >>> On Fri, Nov 9, 2012 at 3:11 PM, Bjorn Helgaas <bhelg...@google.com> >> >>> wrote: >> >>>> [+cc Greg, Peter, Tony since they acked the original patch [1]] >> >>>> >> >>>> On Thu, Nov 8, 2012 at 1:04 PM, Mika Westerberg >> >>>> <mika.westerb...@linux.intel.com> 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?
I'm certainly not. I agree with adding it to struct device now and replace it later if someone designs something better. I also agree with using a dev_acpi_node() macro as you described above. I went the opposite way with device tree, and I absolutely regret it. g. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
