ADMtek AL981 "Comet" chipset. The AL981 is yet another DEC tulip clone,
except with simpler receive filter options. The AL981 has a built-in
transceiver, power management support, wake on LAN and flow control.
This chip performs extremely well; it's on par with the ASIX chipset
in terms of speed, which is pretty good (it can do 11.5MB/sec with TCP
easily).
I would have committed this driver sooner, except I ran into one problem
with the AL981 that required a workaround. When the chip is transmitting
at full speed, it will sometimes wedge if you queue a series of packets
that wrap from the end of the transmit descriptor list back to the
beginning. I can't explain why this happens, and none of the other tulip
clones behave this way. The workaround this is to just watch for the end
of the transmit ring and make sure that al_start() breaks out of its
packet queuing loop and waiting until the current batch of transmissions
completes before wrapping back to the start of the ring. Fortunately, this
does not significantly impact transmit performance.
This is one of those things that takes weeks of analysis just to come
up with two or three lines of code changes.
-------------------------------------------------------------------------------
Recent versions of 3.0-current have the bktr driver built in. Older versions
of 3.0 and all versions of 2.2 need to have the driver files installed by hand:
cp ioctl_bt848.h /sys/i386/include/
cp brktree_reg.h brooktree848.c /sys/pci/
In /sys/conf/files add:
pci/brooktree848.c optional bktr device-driver
-------------------------------------------------------------------------------
In all cases you will need to add the driver to your kernel:
In your kernel configuration file:
controller pci0 #if you already have this line don't add it.
device bktr0
There is no need to specify DMA channels nor interrupts for this
driver.
-------------------------------------------------------------------------------
Finally you need to create nodes for the driver:
Create a video device:
mknod /dev/bktr0 c 92 0
Create a tuner device:
mknod /dev/tuner0 c 92 16
-------------------------------------------------------------------------------
The code attempts to auto-probe code to detect card/tuner types.
The detected card is printed in the dmesg as the driver is loaded. If
this fails to detect the proper card you can override it in brooktree848.c:
#define OVERRIDE_CARD <card type>
where <card type> is one of:
CARD_UNKNOWN
CARD_MIRO
CARD_HAUPPAUGE
CARD_STB
CARD_INTEL
-------------------------------------------------------------------------------
This model now separates the "tuner control" items into a minor device:
minor device layout: xxxxxxxx xxxT UUUU
UUUU: the card (ie UNIT) identifier, 0 thru 15
T == 0: video device
T == 1: tuner device
Access your tuner ioctl thru your tuner device handle and anything
which controls the video capture process thru the video device handle.
Certain ioctl()s such as video source are available thru both devices.
-------------------------------------------------------------------------------
If your tuner does not work properly or is not recognized properly
try setting the tuner type via or card type:
sysctl -w hw.bt848.card=<integer> current valid values are 0 to 5 inclusive
sysctl -w hw.bt848.tuner=<integer> where integer is a value from 1 to 10
systcl -w hw.bt848.reverse_mute=<1 | 0> to reverse the mute function in the
driver set variable to 1.
The exact format of the sysctl bt848 variable is:
unit << 8 | value
unit identifies the pci bt848 board to be affected 0 is the first bt848
board, 1 is the second bt848 board.
value denotes the integer value for tuners is a value from 0 to 10 for
reversing the mute function of the tuner the value is 1 or 0.
to find out all the bt848 variables:
sysctl hw.bt848
-------------------------------------------------------------------------------
The bt848 driver consists of:
src/sys/i386/include/ioctl_bt848.h
src/sys/pci/brktree_reg.h
src/sys/pci/brooktree848.c
ab431312b4