Toshiba LANCT00A PC Card

When I was in Akihabara last, I got a lot of PC Cards from the junk vendors for 100 Yen. One of these cards was the Toshiba LANCT00A. This card didn't probe when I first got it. FreeBSD didn't support it. This was a challenge.

As long-time reads of this blog may know, I sometimes go out of my way to hack on really oddball hardware that somehow I get it into my head needs to work. Never mind that I have a dozen other projects cooking that is more relevant to FreeBSD and its user base. Never mind that some of this hardware was obsolete when I started hacking on FreeBSD's PC Card layer. The cool thing is that I can find just enough documentation to be interesting on these cards.

This Toshiba card was like that. Google searches for information about it turned up a half dozen posts to different FreeBSD and Linux mailing lists asking about it, plus some speculation about what's in the card. One brave soul even took his card apart and reported it had a NS DP83902 under the hood. However, nobody that I can find ever got this card working under FreeBSD or Linux. Checks of the current Linux kernel was no help. Checks of OpenBSD and NetBSD also yielded no results. There was a windows driver available (actually an NDIS driver of unknown version).

So I was printing out random values for this card. At one time the FreeBSD PC Card probe routine for ed tried to probe WD80x3 cards as well as NE2000 cards. I removed this about 4 years ago after failing to find any cards that needed this, used it, etc. However, this card is almost a WD80x3 clone. I was printing the board type in the attach routine, trying to track down why attach was failing. I saw that it was 20 decimal or 0x14. A quick scan of the if_edreg.h file showed this was one of the Toshiba cards. The comments said it was a PCETC board. I immediately thought "Hmmm, isn't this a Toshiba card?" and then wondered if the 'C' in LANCT00A meant it was the same silicon revision as the 'C' in the PCETC. So I hacked up a quick little test into the if_ed_pccard probe routine.

It recognized it the card when I did that! Success. Well, almost. There was a snag. The memory allocated for this card was at 0x88000000. This didn't pass through the sanity test in the driver designed for ISA cards, so it didn't work. A little more hacking and I was getting a sane MAC address and the card was attaching. It dhcped its address w/o incident.

However, all is not right in mudville. As soon as I started using TCP, I started getting sbdrop panics. It looks like the packets that the WD80x3 code is pumping out aren't quite rightly aligned, or something (I have never had a sbdrop panic, so I'll have to investigate what that means when I have some time). This isn't too terribly surprising, since I haven't tested the ISA cards in years. Maybe something broke for the memory copyout path, but not for the PIO copyout path. I'll have to track that down another night.

[[ UPDATE: It looks like it was the copyin path. There was a bug in it that caused 2x too many bytes to be read into memory, causing the corruption. So now it works well enough for me to update this post and commit the change. ]]

Now, what does this gain FreeBSD? Not much, in the grander scheme of things. I'd be surprised if any of my readers actually had one of these cards and started using it as a result of my work. However, it was a relaxing hour or two of my life. Given my current job stress level, this has great value to me. Also, I think this is one of the first PC Cards to work with both I/O and Memory windows mapped at the same time from the CFE entry. While there are some other cards that manually allocate memory ranges, I don't think any of them have it in their CIS.

Postscript

Well, while I was doing research for this blog entry, I stumbled accross http://linux.toshiba-dme.co.jp/linux/eng/download.htm which has a tos_cs for download. There's a lot of voodoo magic in that driver that I'll have to investigate. This driver is 1000 lines long, and was for Linux 2.0.35. It was never integrated into Linux, so I'd stand by my statement that Linux doesn't support it. Just for kicks I tried building it under 2.6.29, and it didn't compile anymore.

My changes to the ed driver in FreeBSD are more like 20-25 lines of code. There's magic kick of a magic offset in shared memory that isn't present in FreeBSD's ed driver today. I'll keep that in mind in case I have the card wedge on me under load or something.