--- shesha bhushan <bhushan_vadulas@hotmail.com> wrote: > 1. pci_map_single will transfer the data from RAM (kernel > area) to the hardware accessible area and will provide > with a pointer which can then be passed to the hardware. > 2. In the above function the "size" parameter indicates > the amount of DMA transfer. > Am I correct in the above two points? If I am wrong please > correct me. pci_map_single() is architecture specific. On Intel i386, it just returns the physical address corresponding to the virtual address passed in as parameter, no copying is done. The size parameter is ignored. > In the Linux Device driver book (page 408), he says, data > must be explicitly flushed from the processor cache. And > data flushed this way is not avaliable to the device. > > This means that we must flush the processor cache before > calling pci_map_single. How can we achieve this. I didn't understand that fully. But I guess the call to flush_write_buffers() in pci_map_single() (again, this is for Intel i386) does what you are looking for. Hope this helps. -Ravi. __________________________________________________ Do you Yahoo!? Yahoo! Shopping - Send Flowers for Valentine's Day http://shopping.yahoo.com -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
