Re: support for sata7 Streaming Feature Set?

From: Tejun Heo
Date: Thu May 18 2006 - 19:18:11 EST

Jeff Garzik wrote:
Mark Lord wrote:
The device driver has to know about it, at a minimum so that it can
select a different EH protocol for the streams. Which in turn means
that the streaming commands should be known to the driver as well.

Different taskfile protocol, you mean?

I haven't checked all the docs and codes thoroughly but I don't see a need for new protocol or anything. When a streaming command fails due to failing to meet timing constraints, it fails w/ device error. sg can adjust retry count and the device error will be reported without much recovery action (only revalidation). If the device fails due to some other reasons (say HSM violation), it needs full EH no matter what. Without full EH, it becomes completely unusable.

But how to handle it all nicely is the real question.
A new block driver, if libata cannot handle it?

I seriously doubt writing a whole new ATA driver subsystem will fly :)

All I can see are little extensions to sg interface and maybe libata. I don't think it needs full-blown in-kernel driver. However, to use this feature with a filesystem, we would need to build a block map of the file to use. I think such feature is already provided and used by LILO/GRUB kinds of things.

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