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SubjectRe: [PATCH] Broadcom 8603 SAS/SATA driver, rough draft
Jeff Garzik wrote:
> Rather than sitting on this for far too long, I wanted to go ahead and
> get this out there. I heard some chips might be trickling out into
> public hands.
>
> This is a bare bones Broadcom 8603 SAS+SATA driver, attempting to use
> the vaunted libsas. Notes:
>
> * A quick glance at the FIXMEs will tell you obviously doesn't work.
>
> * The hardware is quite simple and straightforward and easy to program
> in an efficient way: each SAS port has a command queue (DMA ring) and
> a response queue (DMA ring). Or if in SATA mode, just a command
> queue.
>
> * The SAS/SATA negotiation is largely out of our hands. The silicon
> does its thing, and then tells us what type of device connected. We
> are then expected to switch the port to either SAS mode or SATA mode,
> accordingly.
>
> * There is no firmware or anything. Just DMA and register bitbanging.
> We have plenty of low-level control.
>
> * The state of SAS/SATA integration is perpetually pathetic. Updates
> in this area are likely. There's a rumor Brian King @ IBM may look
> into this area too.
>
> * This driver pretty much completely lacks exception handling.
>
>
> As an aside, I am also writing a driver for Marvell chips that behave
> quite similarly to this chip. It seems the future of storage might look
> like these Broadcom and Marvell SAS+SATA DMA ring interfaces, in the
> volume marketspace at least.

Jeff,
Is the lack of SMP support a driver limitation or is it
the silicon?

How about support for wide ports (i.e. when 2 or more HBA
phys are attached to remote phys which have the same SAS
addresses)?

Last question: can the chip run in SCSI target mode?

Doug Gilbert
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