ldi_open_by_devid(9F) (man pages section 9: DDI and DKI Kernel Functions)

man pages section 9: DDI and DKI Kernel Functions

ldi_open_by_devid(9F)

Name

ldi_open_by_dev, ldi_open_by_name, ldi_open_by_devid, ldi_close– open and close devices

Synopsis

#include <sys/sunldi.h> 

int ldi_open_by_dev(dev_t *devp, int otyp, int flag, cred_t  *cr, 
     ldi_handle_t *lhp, ldi_ident_t li);

int ldi_open_by_name(char  *pathname, int flag, cred_t *cr, 
     ldi_handle_t *lhp, ldi_ident_t li);

int ldi_open_by_devid(ddi_devid_t devid, char  *minor_name, int flag,
     cred_t *cr, ldi_handle_t *lhp, ldi_ident_t li);

int ldi_close(ldi_handle_t lh, int flag, cred_ t *cr);

Parameters

lh

Layered handle

lhp

Pointer to a layered handle that is returned upon a successful open.

li

LDI identifier.

cr

Pointer to the credential structure used to open a device.

devp

Pointer to a device number.

pathname

Pathname to a device.

devid

Device ID.

minor_name

Minor device node name.

otyp

Flag passed to the driver indicating which interface is open. Valid settings are:

OTYP_BLK: Open the device block interface.
OTYP_CHR: Open the device character interface.

Only one OTYP flag can be specified. To open streams devices, specify OTYP_CHR.

flag

Bit field that instructs the driver on how to open the device. Valid settings are:

FEXCL: Open the device with exclusive access; fail all other attempts to open the device.
FNDELAY: Open the device and return immediately. Do not block the open even if something is wrong.
FREAD: Open the device with read-only permission. (If ORed with FWRITE, allow both read and write access).
FWRITE: Open a device with write-only permission (if ORed with FREAD, then allow both read and write access).
FNOCTTY: Open the device. If the device is a tty, do not attempt to open it as a session-controlling tty.

Description

The ldi_open_by_dev(), ldi_open_by_name() and ldi_open_by_devid() functions allow a caller to open a block, character, or streams device. Upon a successful open, a layered handle to the device is returned via the layered handle pointed to by lhp. The ldi identifier passed to these functions is previously allocated with ldi_ident_from_stream(9F), ldi_ident_from_dev(9F), and ldi_ident_from_dip(9F).

The ldi_open_by_dev() function opens a device specified by the dev_t pointed to by devp. Upon successful open, the caller should check the value of the dev_t to see if it has changed. (Cloning devices will change this value during opens.) When opening a streams device, otyp must be OTYP_CHR.

The ldi_open_by_devid() function opens a device by devid. The caller must specify the minor node name to open.

The ldi_open_by_name() function opens a device by pathname. Pathname is a null terminated string in the kernel address space. Pathname must be an absolute path, meaning that it must begin with '/'. The format of the pathname supplied to this function is either a /devices path or any other filesystem path to a device node. Opens utilizing /devices paths are supported before root is mounted. Opens utilizing other filesystem paths to device nodes are supported only if root is already mounted.

The ldi_close() function closes a layered handle that was obtained with either ldi_open_by_dev(), ldi_open_by_name(), or ldi_open_by_devid(). After ldi_close() returns the layered handle, the lh that was previously passed in is no longer valid.

Return Values

The ldi_close() function returns 0 for success. EINVAL is returned for invalid input parameters. Otherwise, any other error number may be returned by the device.

The ldi_open_by_dev() and ldi_open_by_devid() functions return 0 upon success. If a failure occurs before the device is open, possible return values are shown below. Otherwise any other error number may be returned by the device.

EINVAL: Invalid input parameters.
ENODEV: Requested device does not exist.
ENXIO: Unsupported device operation or access mode.

The ldi_open_by_name() function returns 0 upon success. If a failure occurs before the device is open, possible return values are shown below. Otherwise any other error number may be returned by the device.

EINVAL: Invalid input parameters.
ENODEV: Requested device path does not exist.
EACCES: Search permission is denied on a component of the path prefix, or the file exists and the permissions specified by cr are denied.
ENXIO: Unsupported device operation or access mode.

Context

These functions may be called from user or kernel context.

These functions should not be called from a device's attach, detach, or power entry point. This could result in a system crash or deadlock.

Notes

Use only OTYP_CHR or OTYP_BLK options when you use the ldi_open_by_dev() and ldi_open_by_devid() functions to open a device. Other flags, including OTYP_LYR, have been deprecated and should not be used with these interfaces.

The caller should be aware of cases when multiple paths to a single device may exist. (This can occur for scsi disk devices if scsi_vhci(7D)) is disabled or a disk is connected to multiple controllers not supported by scsi_vhci(7D).

In these cases, ldi_open_by_devid() returns a device handle that corresponds to a particular path to a target device. This path may not be the same across multiple calls to ldi_open_by_devid(). Device handles associated with the same device but different access paths should have different filesystem device paths and dev_t values.

In the cases where multiple paths to a device exist and access to the device has not been virtualized via MPXIO (as with scsi disk devices not accessed via scsi_vhci(7D)), the LDI does not provide any path fail-over capabilities. If the caller wishes to do their own path management and failover they should open all available paths to a device via ldi_open_by_name().

SunOS 5.11 Last Revised 9 Aug 2004