Hello everybody ! I have 2 question about how DMA work, especially for PCI devices.
The first one concerns the device. How can i know if a device is DMA-able ? I found a function in the kernel source code called 'dma_set_mask'. I want to know which registers of the device this function sets, and how it sets it : via Port I/O or MMIO, and where i can find the address where it is written ? I browsed the code, but i did not managed to see from which register inside a pci device are involved. The second question concern the DMA principles (precisely DMA Bus Mastering). For the question, let's make the supposition that we want to make a transfert from a device to RAM. How do i specify the memory address of the device from where i need to copy data of a specified length to the DMA buffer? How do i know where the data to be transfered begin ? In most of the documents describing a driver with DMA, they never specify that point. If someone can light me on those two points, that would help me a lot in my work. Fernand. -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to [email protected] Please read the FAQ at http://kernelnewbies.org/FAQ
