On Monday, November 19, 2012 06:32:06 PM Rafael J. Wysocki wrote: > On Monday, November 19, 2012 08:23:34 AM Greg Kroah-Hartman wrote: > > On Sun, Nov 18, 2012 at 10:13:59PM +0100, Rafael J. Wysocki wrote: > > > From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> > > > > > > The current platform device creation and registration code in > > > acpi_create_platform_device() is quite convoluted. This function > > > takes an ACPI device node as an argument and eventually calls > > > platform_device_register_resndata() to create and register a > > > platform device object on the basis of the information contained > > > in that code. However, it doesn't associate the new platform > > > device with the ACPI node directly, but instead it relies on > > > acpi_platform_notify(), called from within device_add(), to find > > > that ACPI node again with the help of acpi_platform_find_device() > > > and acpi_platform_match() and then attach the new platform device > > > to it. This causes an additional ACPI namespace walk to happen and > > > is clearly suboptimal. > > > > > > Use the observation that it is now possible to initialize the ACPI > > > handle of a device before calling device_add() for it to make this > > > code more straightforward. Namely, add a new field to struct > > > platform_device_info allowing us to pass the ACPI handle of interest > > > to platform_device_register_full(), which will then use it to > > > initialize the new device's ACPI handle before registering it. > > > This will cause acpi_platform_notify() to use the ACPI handle from > > > the device structure directly instead of using the .find_device() > > > routine provided by the device's bus type. In consequence, > > > acpi_platform_bus, acpi_platform_find_device(), and > > > acpi_platform_match() are not necessary any more, so remove them. > > > > Why can't you use the platform_data * that is already in struct device > > for this, instead of adding an acpi-specific field to the > > platform_device structure? > > Hmm, I kind of don't understand the question. :-) > > Yes, we have acpi_handle in struct device (it actually is being added by a > patch you've acked) and we use it. The whole point here is to streamline > of the initalization of that field. > > > If not that, surely there is another field in struct device that you > > could use that is free for this type of device? > > Yes, there is one and as I said above. :-) > > I'd be happy to use the struct device's field directly, but > platform_device_register_full() allocates memory for the struct device in > question, so that field actually doesn't exist yet when it is called. So what happens is we want to use platform_device_register_full(), because it initializes a struct platform_device for use and registers it for us, so we don't need to worry about all that. However, platform_device_register_full() also creates the struct platform_device it registers and we need to let it know what value to put into the acpi_handle field of that struct platform_device object's struct device component. That's what this all is about. :-) 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
