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    SubjectRe: [PATCH 09/10] MCDE: Add build files and bus
    On Tue, Nov 30, 2010 at 10:05:50PM +0000, Russell King - ARM Linux wrote:
    > On Tue, Nov 30, 2010 at 10:48:34AM -0800, Greg KH wrote:
    > > On Tue, Nov 30, 2010 at 06:40:49PM +0000, Russell King - ARM Linux wrote:
    > > > There's lots of static devices, not only platform devices, in the ARM
    > > > tree. It's going to be a hell of a lot of work to fix this all up
    > > > properly.
    > >
    > > I agree, it's been abused for many years this way :(
    >
    > I don't agree that it is abuse - it was something explicitly allowed by
    > the original device model design by Patrick, with the condition that
    > such a device was never unregistered. That's exactly the way we treat
    > these devices.

    I understand Pat allowed this, I just don't agree that it's the correct
    thing to do :)

    -mm had a patch for a long time that would throw up warnings if you ever
    did this for x86 so that arch should be clean of this issue by now.

    > What I'm slightly concerned about is that this is going to needlessly
    > bloat the kernel - we're going to have to find some other way to store
    > this information, and create devices from that - which means additional
    > code to do the creation, and data structures for it to create these from.
    > There will be additional wastage from kmalloc as kmalloc doesn't allocate
    > just the size you ask for, but normally a power of two which will contain
    > the size.
    >
    > That could potentially mean that as the device structure is 216 bytes,
    > kmalloc will use the 256 byte allocation size, which means a wastage of
    > 40 bytes per device structure. On top of that goes the size of
    > resources with the allocation slop on top for that, and then there's
    > another allocation for the platform data.
    >
    > Has anyone considered these implications before making this choice?

    Yes, I have, which is one reason I haven't done this type of change yet.
    I need to figure out a way to not drasticly increase the size and still
    make it easy and simple for the platform and driver write their code.

    It's a work in progress, but wherever possible, I encourage people to
    not make 'struct device' static.

    thanks,

    greg k-h


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