On Monday 25 March 2002 21:25 pm, Kevin Pedretti wrote: > The reason I ask is that I'm working on/modifying a set of modules that > accesses user space from interrupt context. I know this is not a good > thing to do generally, but for performance reasons the original author > wanted to copy directly into a mlocked user space buffer from a network Some drivers (I know for sure about OSS drivers) do it the opposite way. The driver allocates a buffer (or usually multiple buffers) in physical memory. The buffers are directly accessible from the device hardware for DMA etc. The interrupt routines normally would not touch the buffers (although they could) but just tell the device how to use the buffers. The user's process that needs to use the device can use the read/write interface, or for better performance mmap the device (which maps the buffers into a contiguous user space) and access the buffers directly. With the mmap api, ioctls are used to tell the process how much new data is available (for reading) or how much was consumed by the device (so these buffers can be written with new data). -- Itai -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
