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Top Forums UNIX for Advanced & Expert Users Experts Only! Hard Question Ahead!!!! Post 12825 by wizard on Monday 7th of January 2002 09:22:04 PM
Old 01-07-2002
All devices in UNIX are accessed as files. Providing this abstraction requires some pretty complicated programming in the kernel. The programs are called device drivers. Once you write a device driver, you must add it to the kernel and make it available to user processes to access the device in question. In the process of incorporating the device driver into the kernel, you add the driver entry points to the device switch table. The device switch table is basically a muti-dimensional array. The major number of a device is the index into the array to access the device driver entry points. The meaning of the device minor number depends on the device driver. It can be used anyway the driver writer wants to use it. However, in most cases, it is used to differentiate between multiple instances of the same type of device.
 

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devfs(7FS)                                                         File Systems                                                         devfs(7FS)

NAME
devfs - Devices file system DESCRIPTION
The devfs filesystem manages a name space of all devices under the Solaris operating environment and is mounted during boot on the /devices name space. The /devices name space is dynamic and reflects the current state of accessible devices under the Solaris operating environment. The names of all attached device instances are present under /devices. The content under /devices is under the exclusive control of the devfs filesystem and cannot be changed. The system may be configured to include a device in one of two ways: By means of dynamic reconfiguration (DR), using, for example, cfgadm(1M). For devices driven by driver.conf(4) enumeration, edit the driver.conf file to add a new entry, then use update_drv(1M) to cause the system to re-read the driver.conf file and thereby enumerate the instance. The device may be attached through a number of system calls and programs, including open(2), stat(2) and ls(1). During device attach, the device driver typically creates minor nodes corresponding to the device via ddi_create_minor_node(9F). If the attach is successful, one or more minor nodes referring to the device are created under /devices. Operations like mknod(2), mkdir(2) and creat(2) are not supported in /devices. FILES
/devices Mount point for devfs file system SEE ALSO
devfsadm(1M), vfstab(4), attach(9E) NOTES
The /devices name space cannot be unmounted. All content at or below the /devices name space is an implementation artifact and subject to incompatible change or removal without notifi- cation. SunOS 5.10 26 Oct 2004 devfs(7FS)
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