Tribblix: manual page: ldi_open_by

LDI_OPEN_BY_DEV(9F) Kernel Functions for Drivers LDI_OPEN_BY_DEV(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(const char *pathname, int flag, cred_t *cr,
ldi_handle_t *lhp, ldi_ident_t li);

int ldi_open_by_devid(ddi_devid_t devid, const 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(4D)) is disabled or a disk is connected to multiple
controllers not supported by scsi_vhci(4D).

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(4D)), 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().

November 21, 2022 LDI_OPEN_BY_DEV(9F)