Oops, accidentally pressed send... On Tue, Jul 5, 2011 at 12:58 PM, Mandeep Sandhu <mandeepsandhu.chd@xxxxxxxxx> wrote: > On Tue, Jul 5, 2011 at 12:29 PM, Paraneetharan Chandrasekaran > <paraneetharanc@xxxxxxxxx> wrote: >> I think the thread originator is asking about how the application knows >> which device file to read or write. >> This is done by h/w management system udev. udev creates/manages device >> nodes in /dev/ dir and notifes applications based on the udev rules written >> (via HAL events or DBUS signals). > > I don't think udev is involved in the read/write file ops. Udev is > responsible for handling hotplug events, doing certain actions based > on events (as indicated by udev rules),persistent naming of devices > etc...but not file i/o. > > That, I think, is handled by the VFS layer. Each device node is > uniquely identified by it's MAJOR-MINOR number combo. I guess the VFS > layer uses this to pick the correct file-ops struct to communicate > with the device. Eg; when we try to open a device, say /dev/ttyS0, it's major-minor numbers (eg: 64-4 on my machine) are used to lookup the file-ops struct and from then on, the VFS passes the read/write calls to this device driver. HTH, -mandeep > > My info is a little dated, so plz CMIIW. > > HTH, > -mandeep > _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
