Eike,
dma_sync_single_for_cpu() takes a 'struct device *', but the device
I'm using with pci_alloc_consistent() is a 'struct pci_dev *'. where do
I get the 'struct device *'? I looked at the pci_dev structure, and it
doesn't seem to have a pertinent member i can use. Should I just
declare one locally?
thanks for helping me through this.
--CB
Rolf Eike Beer wrote:
Charles Brown wrote:
Eike,
A followup on the pci_alloc_consistent. Once the hardware has
deposited data into the buffer, how do I copy out of that buffer into a
user space buffer? memcpy_fromio? Do I need to ioremap it, first?
something like;
// get memory that is usable by DMA
outmem = pci_alloc_consistent(pdev, PAGE_SIZE, &outmem_phys);
// tell board about it
memcpy_toio(dest + 4, &outmem_phys, sizeof(outmem_phys));
Nope, it's easier: pci_alloc_consistent() will return you 2 addresses: the
physical one (which you pass to the device) and the "software" one, i.e. what
the kernel can see. When you notice that your device is finished you call
dma_sync_single_for_cpu() to make sure will be accessible by your CPU(s)
(caches and the like need to be noticed) and then you can simply memcpy() from
your kernel buffer to whereever you like.
Eike
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