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TMCHGIMPARM (Change Parameters) tmssa Device Driver ioctl Operation
Purpose
To allow the caller to change the retry parameter and the time out parameter that are
used by the target-mode device driver.
Description
This operation allows the caller to change the default set up of the device. It is allowed
only for the initiator-mode device. The arg parameter to the TMCHGIMPARM operation
contains the address of the tm_chg_im_parm structure that is defined in the
/usr/include/sys/tmscsi.h file.
Default values that are used by the device driver for the retry parameter and for the
time out parameter usually do not require change. For some calling programs, however,
default values can be changed to fine tune timing parameters that are related to error
recovery.
When a parameter is changed, it remains changed until another TMCHGIMPARM
operation occurs, or until the device is closed. When the device is opened, the
parameters are set to the default values.
Parameters that can be changed with this operation are:
v The delay (in seconds) between device-driver-initiated retries of send commands
(the retry parameter)
v The time allowed before the write operation times out (the time out parameter).
To indicate which of the possible two parameters the caller is changing, the caller sets
the appropriate bit in the chg_option field. The caller can change either the retry
parameter, or the time out parameter, or it can change both parameters.
To change the delay between send command retries, the caller sets the
TM_CHG_RETRY_DELAY flag in the chg_option field and puts the required delay value
(in seconds) into the new_delay field of the structure. With this command, the retry
delay can be changed to any value 0 through 255, where 0 instructs the device driver
to use as little delay as possible between retries. The default value is approximately two
seconds.
To change the send command time-out value, the caller sets the
TM_CHG_SEND_TIMEOUT flag in the chg_option field, sets the desired flag in the
timeout_type field, and puts the desired time-out value into the new_timeout field of the
structure. One flag must be set in the timeout_type field to indicate the required form of
the time-out. If the TM_FIXED_TIMEOUT flag is set in the timeout_type field, the value
that is put into the new_timeout field is a fixed time-out value for all send commands. If
the TM_SCALED_TIMEOUT flag is set in the timeout_type field, the value that is put
into the new_timeout field is a scaling-factor used in the calculation for time-outs as
shown under the description of the write entry point. The default send command
time-out value is a scaled time-out with a scaling factor of 20.
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