Messages in this thread | | | From | Grant Likely <> | Subject | Re: [PATCH] of: use platform_device_add | Date | Thu, 22 Nov 2012 21:19:09 +0000 |
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On Wed, 21 Nov 2012 10:34:03 -0800, Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote: > On Wed, Nov 21, 2012 at 06:15:59PM +0000, Grant Likely wrote: > > This allows platform_device_add a chance to call insert_resource on all > > of the resources from OF. At a minimum this fills in proc/iomem and > > presumably makes resource tracking and conflict detection work better. > > However, it has the side effect of moving all OF generated platform > > devices from /sys/devices to /sys/devices/platform/. It /shouldn't/ > > break userspace because userspace is not supposed to depend on the full > > path (because userspace always does what it is supposed to, right?). > > > > It also has a backup call to of_device_add() when running on PowerPC to > > catch any devices that have overlapping regions. It will complain about > > them, but it will not fail to register the device. > > > > Cc: Jason Gunthorpe <jgunthorpe@obsidianresearch.com> > > Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> > > Cc: Rob Herring <rob.herring@calxeda.com> > > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > > Signed-off-by: Grant Likely <grant.likely@secretlab.ca> > > --- > > > > Greg, do you mind taking a look at this? The reason the OF code hasn't been > > calling platform_device_add() directly to this point is: > > a) there are some trees with resource overlays > > b) I want the devices in /sys/devices not /sys/devices/platform. > > Putting the devices all in the "flat" location of /sys/devices/ is a bit > worrisome to me. What's wrong with platform/ ? That is what they are, > right? Why change this?
Hahaha. *You* encouraged me to write the patch to remove /sys/devices/platform/ when I was waffling over whether or not it was a good idea. Granted, that was well over a year ago, but it takes me a while to get around to some of the things on my todo list. :-)
It's not so much that there is anything wrong with platform/ other than it is nonsensical. For example, a core system bus is often represented by an platform device of it's own with a bunch of peripherals as children of that. For example a PCI host controller. It doesn't make much sense to me for some core devices to be at /sys/devices and others to be gathered together under /sys/devices/platform.
However, all that mildly feels 'wrong' to me but isn't that big deal. A bigger problem with b) (which I didn't describe well) is that existing PowerPC support roots the platform devices hierarchy at /sys/devices, not /sys/devices/platform and I'm nervous that changing it will break things. If I commit the change that makes the move, and somebody complains that I broke their userspace, then I need to have an exception for those system or revert the patch entirely.
Regardless, I'm no longer happy with DT and non-DT platform device registration having separate code paths. I would /like/ for sys/device/platform to disappear, but that is merely a side issue. The real issue is whether or not existing PowerPC userspace breaks. If it does, there needs to be an exception to keep things under /sys/devices.
> > I could easily add exceptions to platform_device_add() for both those cases, but > > I don't like adding DT exceptions to the common code. However, I still need to > > support the platforms that unfortunately have overlapping resources. This patch > > does that by still calling the old path if platform_device_add() fails, but it > > isn't nice either because of_device_add() has to duplicate > > platform_device_add(). Blech. Plus the exception only applies for PowerPC. > > > > So, how do you feel about having a 'relaxed' mode for platform_device_add() > > which means it won't fail if resources overlap and maybe won't do the silly > > platform_bus parent thing. Thoughts? > > I have no objection for the resource issue, if you assure me it will not > be abused :)
I can make that assurance. It will be powerpc-only also.
g.
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