Hello, thanks for your comments.
Am Mittwoch, den 25.10.2006, 11:28 +0900 schrieb David Cournapeau: > Andrew Straw wrote: > > David Cournapeau wrote: > > > >> I don't know anything about your device, but a driver directly accessing > >> a memory buffer from a userland program sounds like a bug to me. > >> > > David, DMA memory (yes, I know thats an example of RAS Syndrome, > > apologies) allows hardware to fill a chunk of RAM and then hand it over > > to a userspace program. In my experience, RAM used for this purpose must > > be pre-allocated, usually in a ring-buffer type arrangement. So this is > > normal operating procedure for something like a frame grabber and not a > > bug at all. > > > What I understood from former emails was that the user is allocating a > memory buffer, and that it gives this memory buffer to the hardware. In > this sense, I don't see how it is possible to avoid kernel panic or > equivalents. If on the contrary, the driver gives you the memory buffer, > then, ok, by eg a mmap-like call, you can access directly the device > memory, but within a range fixed by the driver, which is valid if the > driver is not buggy. The API of the camera provides a function pl_exp_start_cont(hCam, buffer, size) The usage is to pass a Camera-Identifier "hCam", a pointer "buffer" and a size "size" in bytes. The camera will then start to acquire frames and put them to the buffer, which has to be size-bytes long. When the function reaches the end of the buffer, it will start at the beginning again (circular buffer mode). There is also a function available to ask for the last buffer position that is written to. The buffer has to be allocated by the caller of this API-function, so I guess it will be in *userland*. To have enough time to read a frame, the buffer has to be sufficiently big. I don't know what is sufficient, but I made it 50 frames big. With an acquisition time of lets say 10ms I have about 0.5seconds to get a frame, that was recently written to the buffer. I know, these things are not numpy and even not Python-questions, but C-questions, and I think I should go and read something about it. Does anyone have a recommendation where to find information on this memory-locking things? How is this kind of programming called? Driver-Programming? Hardware-Programming? System-Programming? Thanks Lars -- Dipl.-Ing. Lars Friedrich Optical Measurement Technology Department of Microsystems Engineering -- IMTEK University of Freiburg Georges-Köhler-Allee 102 D-79110 Freiburg Germany phone: +49-761-203-7531 fax: +49-761-203-7537 room: 01 088 email: [EMAIL PROTECTED] ------------------------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 _______________________________________________ Numpy-discussion mailing list Numpy-discussion@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/numpy-discussion
