Using RealTek interrupts

1
Using RealTek interrupts

• We construct a prototype driver that supports
  receiving of network packets

2
Interrupt Mask Register
15 14 13
6 5 4 3 2 1 0
S E R R
T i m e O u t
L e n C h g
reserved
R X F O V F
P U N / L C
R X B O V F
T E R
T O K
R E R
R O K
0x3C
Legend ROK (Received OK packet) TOK
(Transmit completed OK) RER (Received Error
packet) TER (Transmit was aborted) RxBOvf
(Receive Buffer Overflowed) SERR (System Error on
PCI bus) RxFOvf (Receive FIFO
Overflowed) LenChg (Cable Length changed)
TimeOut (Timer Count Timer Intr) PUN/LC
(Packet Underrun/Link Changed) (0 masked,
1unmasked)
3
Interrupt Status Register
15 14 13
6 5 4 3 2 1 0
S E R R
T i m e O u t
L e n C h g
reserved
R X F O V F
P U N / L C
R X B O V F
T E R
T O K
R E R
R O K
0x3E
Legend ROK (Received OK packet) TOK
(Transmit completed OK) RER (Received Error
packet) TER (Transmit was aborted) RxBOvf
(Receive Buffer Overflowed) SERR (System Error on
PCI bus) RxFOvf (Receive FIFO
Overflowed) LenChg (Cable Length changed)
TimeOut (Timer Count Timer Intr) PUN/LC
(Packet Underrun/Link Changed) (0
inactive, 1active) NOTE An active bit is
cleared by writing 1 to that bit
4
A code walkthrough

• We have written an initial prototype for a
  character-mode device-driver for the 8139
• It supports packet-reception (w/ interrupts)
• A companion application (nicread.cpp) is useful
  for testing this device driver
• We will walk through the drivers design
• Can you spot any bugs in this driver?
• Can you implement packet-transmission?