On 06/01/2011 07:52 AM, Eduard - Gabriel Munteanu wrote:
The main selling point is there are more chances to screw up if every bus layer implements these manually. And it's really convenient, especially if we get to add another ld/st.
If we drop the ld/st, we're talking about 5 lines for every bus layer.
If I recall, there was just the one driver that actually uses the ld/st interface; most used the read/write interface.
If I understand correctly you need some sort of shared state between IOMMUs or units residing on different buses. Then you should be able to get to it even with this API, just like I do with my AMD IOMMU state by upcasting. It doesn't seem to matter whether you've got an opaque, that opaque could very well be reachable by upcasting.
Did I get this wrong?
Can you honestly tell me that
+static int amd_iommu_translate(DMADevice *dev,
dma_addr_t addr,dma_addr_t *paddr,dma_addr_t *len,int is_write)+{
- PCIDevice *pci_dev = container_of(dev, PCIDevice, dma);
- PCIDevice *iommu_dev = DO_UPCAST(PCIDevice, qdev, dev->mmu->iommu);
- AMDIOMMUState *s = DO_UPCAST(AMDIOMMUState, dev, iommu_dev);
THREE (3) upcasts is a sane to write maintainable software? The margin for error here is absolutely enormous.
If you had just passed in that AMDIOMMUState* as the opaque value, it would be trivial to look at the initialization statement and the callback function to verify that the right value is being passed.
r~