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Annotation of driverkit/notes/msg_send_problems, revision 1.1

1.1     ! root        1:                        driverkit msg_send notes
        !             2:                        
        !             3: thread.ipc_kernel TRUE ==> "body of message is in kernel pmap" (avoids copyin
        !             4:        and copyout)
        !             5: task.kernel_ipc_space TRUE ==> ports are kernel objects, i.e., they are 
        !             6:        ptrs to struct kern_port_t instread of ints.
        !             7:        
        !             8: difference between msg_send() and msg_send_from_kernel():
        !             9:        -- msg_send() does copyin() of entire msg body (instead of bcopy())
        !            10:        -- msg_send_from_kernel() forces both ipc_kernel and kernel_ipc_space
        !            11:           TRUE
        !            12:           
        !            13: Must do msg_send_from_kernel() if it's possible that current_task() is a user task. For example, the exported methods in SCSIController call enqueueCmd, which will do a msg_send to cmdPort. No good - the msg_send() will do a copyin() to get a local copy of the message body; the copyin() willget garbage from the user task. Thus SCSIController has to keep a kern_port_t version of cmdPort; enqueueCmd will do a msg_send_from_kernel to that.
        !            14: 
        !            15: Other msg_send()s in kernel drivers which need to be msg_send_from_kernel:
        !            16: 
        !            17:     adbDriver:
        !            18:        threadOpCommon in adbDriver.m - same fix (cmdPort)
        !            19:        fake_hw_intr_msg() in adbArch.m - same fix (interruptPort)
        !            20:     SCSIController:
        !            21:        enqueueCmd in SCSIControllerPrivate (cmdPort)
        !            22:        FAKE_HARDWARE version of enableInterrupt in SCSIDevice.m 
        !            23:                (interruptPort) <<<probably can skip....>>
        !            24:     Ethernet:
        !            25:        enetNotifyThread in Ethernet.m (IOPort)
        !            26:        enetSyncCmd in Ethernet.m (IOPort)
        !            27:        
        !            28: msg_send()s which are OK as is:
        !            29:     SCSIController:
        !            30:        SCSITimerFcn (timerPort) - called via IOTimeout
        !            31:     libIO:
        !            32:        iotaskTest() - this is an IOTask thread.
        !            33:        

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