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/ > 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. 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. My mockup code that keeps keeps the hardware block id in the platform device arch specific data works well since the hardware block id with value zero is a special case. The value zero means "external non-soc device", so a "regular" board specific struct platform_device that do not setup arch specific data can just be skipped in idle()/wakeup(). If you guys dislike adding arch specific data to struct platform device then for SuperH we can just (mis)use the arch specific data in struct device instead. I'm afraid that solution wastes memory since the data will only be used for platform devices anyway. So I prefer adding arch specific data to struct platform_device instead of struct device if possible. Maybe there are better ways to solve this? I think arch specific data in struct platform_device is pretty straight forward though. Thanks, / magnus _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
