I am working on a device driver that must accept the HDIO_DRIVE_CMD IOCTL. I recognize that this is a tricky operation that subverts the usual block driver request mode of operation. Unfortunately, the device targeted by the ioctl is only part of a much larger system of devices using the same IDE type of driver and normal READ/WRITE requests. In fact, there may be READ or WRITE commands in this device's request queue already. In light of this fact, it is obvious that I can't simply start doing I/O operations from the reception of the ioctl. That means that I will need to enter the drive command in the request queue from within the device driver. While this does not appear to be a trivial matter, there appeared, at first, to be nothing magic about making a request from within the queue. The problem began to get complicated when I realized that requests are filtered for READ, READA, and WRITE commands. The READ and WRITE services in my driver provide exactly that, read block and write block operations...period. I suppose it would be possible to somehow encode the drive command operation within either or both od these operations, but I would like to avoid this if at all possible. I looked at the code in rw_ll_block.c and sched.c to see how Linux handles the requests in the hope that I could make a similar function or set of functions. It appears that entering a request on the request queue is anything but simple. I also tried to figure out how this was being accomplished in the ide.c code., and even thought I understood what was being done there. Alas my poor attempt to emulate this not only failed, but seemed to kill the queue. The lack of a worthwhile kernel debugger doesn't help matters. I am presently against a block wall, and would very much appreciate any constructive suggestions. _________________________________________________________ Do You Yahoo!? Get your free @yahoo.com address at http://mail.yahoo.com -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
