Node -- device node definitions for a device driver


One of the Installable driver/Tunable Parameters kernel configuration files, a Node file, contains definitions used by the idmknodd(ADM) command to create the device nodes (block and character special files) associated with a device driver module. When the Node component of a module's Driver Software Package (DSP) is installed, idinstall(ADM) stores the driver's Node file information in /etc/conf/node.d/module-name, where module-name is the name of the driver being installed. Package scripts should never access /etc/conf/node.d files directly; the idinstall command should be used instead.

Beginning with DDI 8, the first non-comment line should be:

   $maxchan x
This specifies the maximum supported channel number for a DDI driver of version 8 or greater, and should be set to the number of device nodes needed per instance of a device, minus 1. This value must match the value passed to the drv_attach(D3) function in the drv_maxchan member of the drvinfo(D4) structure.

For example, an 8-port serial board usually requires at least 16 nodes, two for each port to indicate modem or non-modem control, so $maxchan would be set to 15.

Drivers that use open redirection (``cloning'') should create one channel for the initial open plus one for each clone channel. See open(D2) for more information about open redirection.

For drivers that use only one channel, set $maxchan 0; channel numbers begin at 0. Use a non-zero value only for drivers that support multiple device files per device instance, such as drivers that support multiple operating modes (such as with or without flow control), or multiple sub-parts (such as slices on a disk).

$maxchan must be specified in the Node file as well as for the drv_attach( ) function because the system must compute the number of channels the driver uses before it can create its special defice node files. The device files must be created before the driver can be opened, and the driver may not be loaded until an open( ) call causes an automatic load, so drv_attach( ) may not be called until after the open( ) occurs.

Following the $maxchan line, if any, must be one or more lines in the following format:

   module-name node-name type channel user group permissions level

All fields are positional and must be separated by white space. The first four fields are required; the last four fields are optional. Blank lines and lines beginning with ````#'''' or ````*'''' are considered comments and are ignored.

The node file fields are:

Identifies the device to which this node applies. The name must match the name specified for the device in the module-name field of the Master(DSP) file, which is also the MODNAME discussed on the Space.c(DSP) manual page.

The device must be defined as a block and/or character device (Master file characteristics flag set to b or c). When the device node is created, the Master file bmaj or cmaj field values will be used as the major number for the created node.

Specifies the name of the node file to be created, relative to /dev. If this field specifies a pathname containing subdirectories, idmknod(ADM) (or, idmknodd(ADM) for DDI 8 drivers) will automatically create these subdirectories.

Beginning with DDI 8, if the name contains %i, one such node file will be created for each instance of this driver's device, with a unique instance number (in variable-width decimal) substituted for the %i. %i is required for DDI 8 drivers prior to UnixWare 7 Release 7.1.

Identifies the type of node to be created. The character b indicates that the node is a block device; the character c indicates character device. The value for this field must match one of the flags specified for the device in the mdevice file characteristics field.

Drivers using a DDI version prior to version 8 may use multiple major numbers. To do this, you specify a value of the form:

where type is the type of node (b or c) and offset gives the offset to this particular device within the range of major numbers specified for this device type in the Master file. For example, the value ``c:2'' refers to a character major offset 2, which, given a major device type specification of ``15-18'', would translate to a character major number of 17.

Specifies the channel number (for DDI 8 or newer drivers) or the minor device number (for older drivers). For entry-type 0 drivers, this field can be coded in one of three ways:

This field is optional. If used, it specifies the user ID of the user that will own the node to be created. The user ID must be specified as a decimal integer value. If user is specified, group and permissions must be specified.

This field is optional. If used, it specifies the group ID of the group that will own the node to be created. The group ID must be specified as a decimal integer value. If group is specified, user and permissions must be specified.

This field is optional. If used, it specifies, in octal form, the permissions for the node to be created, as given to the chmod(C) command (for example, 0777). If permissions is specified, user and group must be specified.

This field is optional. If used, it specifies the level of security to be assigned to the node to be created. The security level must be specified as a decimal integer value. If the Enhanced Security Utilities are not installed, or if the file system containing /dev is a non-MAC file system, this field is ignored.



config(D2) in the HDK documentation set.

``Device instance'' in HDK Technical Reference in the HDK documentation set.


The following sample Node file entries are provided as coding examples.

Make character device files /dev/tty0s, /dev/tty0h, /dev/tty1s, /dev/tty1h, and so forth for a DDI 8 driver, foo:

   $maxchan 1
   foo  tty%is  c  0
   foo  tty%ih  c  1

Make pre-DDI 8 character device iasy using minor device 0:

   iasy  tty00  c  0

Make pre-DDI 8 /dev/net/nau/clone for character device clone. The minor device number is set to the major device number of device nau:

   clone  net/nau/clone  c  nau

For a pre-DDI 8 driver, make /dev/imx586_1 for character device clone. The minor device number is set to the major device number of device imx586 plus 1:

   clone imx586_1  c:1  imx586

For a DDI 8 or later driver that supports 8 device instances per board, there must be 8 device files for each board. The following Node file causes these devices to be created:

   $maxchan 7
   mymodname mydev%i/0 c 0
   mymodname mydev%i/1 c 1
   mymodname mydev%i/2 c 2
   mymodname mydev%i/3 c 3
   mymodname mydev%i/4 c 4
   mymodname mydev%i/5 c 5
   mymodname mydev%i/6 c 6
   mymodname mydev%i/7 c 7
A user-level process can then open the /dev/mydev<N>/<session_number>file, which calls the driver associated with mymodname. The driver is called with the idata for the selected board and the channel number set to the session number. N is a unique number assigned by the system to each new board; no assumptions should be made about the order in which these numbers will be assigned, but once assigned, they will stay the same at least until a reboot. The system will try to keep board instance numbers the same across reboots as well, but if the hardware and/or hardware configuration changes significantly, the system may not be able to preserve the numbers.

The idata is returned by the CFG_ADD subfunction of the config(D2) entry point routine.

02 June 2005
© 2005 The SCO Group, Inc. All rights reserved.
SCO OpenServer Release 6.0.0 - 02 June 2005