Messages in this thread |  | | | Date | Tue, 11 Aug 2009 11:40:25 +0200 | | From | "Emilio G. Cota" <> | | Subject | Re: [patch 2/5] Staging: vme: add VME userspace driver |
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Martyn Welch wrote: > suggest if you want something more complex that allows the user to just > pick a location/size and not worry about windows at all
That's exactly the whole point. I think each bridge should manage its resources; putting this on the upper layer would mean the layer should have a mechanism of 'discovering' what the bridge can/can't do. Anyway this could be revisited later. I'm preparing a patch for this.
>> - Most accesses are 32-bit accesses. Treating all of them >> as 64-bit accesses would decrease performance for most of >> them--which happen to be 32-bit. > I'm not - I'm storing them as 64-bit values, which they are, in the > structures used in *software*. These are then split *when* a write to > the hardware registers is required. Similarly, when the registers are > occasionally read they are combined and stored as a 64-bit value. This > simplifies all *software* checking and manipulation. By storing these as > 2 32-bit values every driver that uses the VME core will need to convert > pci addresses, vme addresses and counts to 2 32-bit values. That is > madness.
I agree with you on that's painful for doing 64-bit accesses. However I'm still not convinced on the performance side (I mean software), since most of the time the upper 32bits will be empty. Will have a look though.
Cheers, E.
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