Date: Fri, 31 Aug 2007 10:30:28 +0530 From: "Prahar Shah" <praharshah123@gmail.com> To: freebsd-net@freebsd.org Subject: Accessing device memory from user-land application process Message-ID: <ebd4dd8d0708302200i77e71fbaxc773da1a0642535b@mail.gmail.com>
next in thread | raw e-mail | index | archive | help
Hi. I am writing a device driver in user-land process. I do a contigmalloc() to allocate the descriptor memory, do a vtophys() on it and mmap that memory in the user-land application process. I allocate buffers again using contigmalloc(), and mmap it within the same process. I pass on a buffer each to the device descriptor. And my packet reception works fine. While processing packets, once i reset the device (all device registers and related memory), and repopulate buffers into the descriptors, I occasionally find that while receiving a packet after reset, the buffer address that I read from the first descriptor is not the one that I gave to the descriptor after the reset. Instead, it turns out to be an older buffer address which as allocated to a descriptor which was supposed to be read next, prior to the reset. My doubt is, could this be a cache-coherency issue? Or could there be a chance that the device might be caching the buffer address available with the descriptors, and re-writing back to the descriptor after receiving the packet, and somehow these cached address are not flushed during a device reset? If i've missed any details, kindly let me know. Any help would be greatly appriciated -- Prahar Shah
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?ebd4dd8d0708302200i77e71fbaxc773da1a0642535b>