On Tuesday 02 June 2009, Kevin Hilman wrote: > Magnus Damm <magnus.damm@xxxxxxxxx> writes: > > > 2009/6/2 Rafael J. Wysocki <rjw@xxxxxxx>: > >> On Monday 01 June 2009, Rafael J. Wysocki wrote: > >>> On Monday 01 June 2009, Magnus Damm wrote: > >>> > From: Magnus Damm <damm@xxxxxxxxxx> > >>> > > >>> > Allow architecture specific data in struct platform_device V2. > >>> > The structure pdev_archdata is added to struct platform_device, > >>> > similar to struct dev_archdata in struct device. > >>> > > >>> > Useful for architecture code that needs to keep extra data > >>> > associated with each platform device. This data shall not > >>> > be accessed by platform drivers, only architecture code. > >>> > > >>> > Needed for platform device runtime PM. > >>> > >>> What exactly do you need this data for? > > > > I'd like to keep a hardware block id associated with each platform > > device on our SoC. > > Please have a look at "PATCH [04/04] sh: Runtime platform device PM mockup", > > http://patchwork.kernel.org/patch/26421/ > > And in OMAP, we will keep a pointer to an SoC-specific struct of > HW specific data to be used in idle/wakeup decision making. > > >> Anyway, I think you can introduce something like: > >> > >> struct <your arch>_platform_device { > >> struct platform_device dev; > >> <some type> <your arch data>; > >> ... > >> }; > >> > >> define your platform devices using the struct above and pass its dev member to > >> the functions that need 'struct platform_device' as an argument. > >> > >> Then you won't need to add arch members to 'struct platform_device' itself. > > > > Thanks for your suggestion. I'm usually a friend of wrapping > > structures and using offsetof(), but in this case I don't think it > > will work very well. > > Neither do I in this case... > > > I'd like to keep a SoC specific hardware block id in this architecture > > specific struct. Then let the arch specific functions > > platform_device_idle() and platform_device_wakeup() use this hardware > > block id to locate which clocks to stop and which power domains to > > fiddle with within the SoC. If we only consider this on-SoC case then > > wrapping and offsetof() works well. > > > > However, a typical embedded system has a wide range of platform > > devices. Some are for the SoC itself and some are for external > > devices, like on board ethernet controlllers (not on chip like the SoC > > platform devices). And since idle() and wakeup() work with struct > > platform device, with a wrapped data structure we need some way to > > check if the platform data is actually wrapped and offsetof() is > > valid. I guess we could use some platform device specific flag for > > this, but that seems overly complicated in my opinion. And modifying > > idle() and wakup() to take arch specific structures is not so good > > since we want to use the same platform driver on multiple > > architectures. > > Also, there many cases where platform_devices are not declared > statically and using the wrapper method doesn't work well if you are > using platform_device_alloc(). In addition to not being able to use > container_of() etc. the memory allocated potentially lasts longer than > the existence of the platform_device. OK, that is a valid point. Best, Rafael _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
