Multi-adapters: what changes the value of PCI_CMD_STAT_REG?

belcon belcon.zhao at
Thu Sep 20 22:41:24 PDT 2007

Hi, all


I tried to test two PCI video cards which used SM501 chips. But I failed to
make them work together. It should be the fault of the driver. The driver
works fine when only one SM501 was actived. I can also find one SM501 can
work together with one Nvidia card. But when two SM501 were set to work
together, the first card displays nothing while the second is ok. The screen
of the first video card was blank. 

I am lucky enough to find why it happens. The command and status register of
the first PCI video card was wrong. It is "0x1c" while the second is "0x1e".
If I set the value to 0x1e, I could see the first screen worked normally. 

Now, the problem is where the driver writes the wrong value into the PCI
configuration space. I had placed xf86DrvMsg() into several functions to
watch the value of PCI_CMD_STAT_REG but found nothing. The value was 0x1e

Anyone can give me a hint? 



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