SI(4)

💖 si(4) — NCR 5380 SCSI bus host adaptor driver 💖

okay so this whole page is from the Kernel Interfaces Manual, and it's the moment for the si and sw drivers. They're literally called "SCSI Weird" and honestly? iconic behavior. 💅

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✨ NAME ✨

si, sw — NCR 5380 SCSI bus host adaptor driver

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🌸 SYNOPSIS 🌸

🧚 sun3

si0 at obio0 addr 0x140000 ipl 2

🧚 sun3 and sun3x

si0 at vme2 addr 0x200000 ipl 2 vect 0x40
si1 at vme2 addr 0x204000 ipl 2 vect 0x41

🧚 sun3/E

sebuf0 at vme2 addr 0x300000 ipl 2 vect 0x74 # and 0x75
sebuf1 at vme2 addr 0x340000 ipl 2 vect 0x76 # and 0x77
si* at sebuf?

🧚 sun4 and sun2

si0 at vme0 addr 0x200000 pri 2 vec 0x40

🧚 sun4/100

sw0 at obio0 addr 0x0a000000 level 3

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🦋 DESCRIPTION 🦋

The si and sw "SCSI Weird" drivers are here to support the NCR 5380 SCSI Bus Controller (SBC) chip. You'll find it on various Sun Microsystems CPU motherboards (obio), and on the "Sun-3 VME SCSI" (Sun part # 501-1236) board used in systems with VME bus. slay. 💖

🍓 sun3 and sun3x

okay so the sun3 and sun3x version of this driver can be configured with a flags directive in the config(1) file. The values are bits in a bitfield, and they're interpreted like this:

• 0x000ff — Set bit (1<<target) to disable SCSI disconnect/reselect.
• 0x0ff00 — Set bit (1<<(target+8)) to disable SCSI parity checking.
• 0x10000 — Set this bit to disable DMA interrupts (poll).
• 0x20000 — Set this bit to disable DMA entirely (use PIO).

Example time: "flags 0x1000f" would disable DMA interrupts, and disable disconnect/reselect for targets 0-3. The target is the SCSI ID number of a particular device on a particular SCSI bus. iykyk. 😌

🌈 sun4

The sun4 version of this driver can also be configured with a flags directive in the config(1) file. The values are bits in a bitfield, and they're interpreted like this:

• 0x01 — Use DMA (may be polled).
• 0x02 — Use DMA completion interrupts.
• 0x04 — Allow SCSI disconnect/reselect.

For example, "flags 0x07" would enable DMA, interrupts, and reselect. By default, DMA is enabled in the sun4 driver. periodt. 💅

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🔥 SEE ALSO 🔥

cd(4), ch(4), intro(4), scsi(4), sd(4), st(4)

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👑 AUTHORS 👑

• David Jones
• Gordon Ross ⟨gwr@NetBSD.org⟩
• Adam Glass ⟨glass@NetBSD.org⟩
• Jason R. Thorpe ⟨thorpej@NetBSD.org⟩.

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💀 BUGS 💀

okay so the VME variant has a bit to enable or disable the DMA engine, but that bit also gates the interrupt line from the NCR5380 (!!). So in order to get any interrupt from the NCR5380, (i.e. for reselect) one must clear the DMA engine transfer count and then enable DMA. This has the further complication that you CAN NOT touch the NCR5380 while the DMA enable bit is set, so we have to turn DMA back off before we even look at the NCR5380. not me crying in DMA 😭

Support for the Sun 4/100 sw "SCSI Weird" is not complete. DMA works, but interrupts (and, thus, reselection) don't for reasons unknown. Further progress has halted pending the availability of a machine for testing. 🙈

DMA, DMA completion interrupts, and reselection work fine on a Sun 4/260 with modern SCSI-II disks attached. There have been reports of reselection failing on Sun Shoebox-type configurations where there are multiple non-SCSI devices behind Emulex or Adaptec bridges. These devices pre-date the SCSI-I spec, and might not behave the way the NCR5380 code expects. For this reason, only DMA is enabled by default in the sun4 driver. 💀

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💌 That's the whole SI(4) page, bestie — source/version Debian, dated May 7, 1998. Bye! 🫶