I have been trying my luck for over a week regarding usage of
'map_user_kiobuf' for doing a DMA into a memory area that belongs to user
Actually my requirement is that I want to do DMA into a user space memory
area. What I have done through suggestions is that allocate memory in user
space. I pass user space buffer address to a kernel module.
Inside the kernel module, I use 'map_user_kiobuf' passing user space buffer
address to it.
After using the 'map_user_kiobuf', I observed the followiing:
1. 'kiobuf->maplist->virtual' contains a different virtual address than
the user space buffer address
2. But these two addresses are mapped as when i write something using the
address 'kiobuf->maplist->virtual' inside the kernel, I see the same
data in the user space buffer in my application.
3. I use the 'virt_to_phys' operation to the virtual address
'kiobuf->maplist->virtual' to get the physical address.
4. I use this physical address for DMA operations.
Now, using this information I do a DMA from card to system memory. What I
have noticed is that DMA happens somewhere else in the system memory. I am
not able to execute most of the commands (ls, chmod, cat, clear etc) after
my user program exits.
Am I doing the steps 3 and 4 above right?
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