Messages in this thread | | | Date | Mon, 06 Sep 1999 12:01:42 +0900 | From | tad-m2n@omoikane ... | Subject | Re: Fixing the SCSI layer |
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Genard wrote: > > - have better sg driver (ex, abort handling, etc) > > What do you want to abort ? Once a command has been passed to the lower > layer, it must complete with or without error, or time out.
Sending abort message to a device.
For expamle, you would want to stop a scanner when it does unwanted and long operation without fail. (recent scanner is fast, though)
Adding message sending handle to SHT would not affect performance, but it make mid-layer bigger...
> I suggest you to invest CAM3 specifications first. The FreeBSD CAM is a > derivative and is very different from official CAM1/3 on some points. It > has also some design/implementation errors in my opinion. > For example, the SIM queuing (CAM3 10.4.2-10.4.3) implementation in > FreeBSD can only have race conditions on error recovery (queue freeze), in > my opinion.
I appreciate good advise. Thanks.
> > step2 : make a 'wrapper' of low driver to the CAM layer. > > Not a good idea, in my opinion. My suggestion is to allow both the CAM > stack and the old SCSI stack to be configured in the kernel, allowing > low-level drivers (SIMs) to be converted when time will allow.
Oh, sorry, I wanted to picture :
-------------------------------------------------------------------- | low | | low specialized to cam mid +-------------------+ | | | wrapped old low | | | ----------------+--------------------------------------------------- | old mid | cam mid | ----------------+--------------------------------------------------- | sd/sr/st/sg | new sd/sr/st/sg + s-net + s-target mode | --------------------------------------------------------------------
(Imagine wrapped old low has limited functionality but enough for sd.)
Ok, I am going to investigate CAM3 and FreeBSD CAM.
Thanks for advise!
-- Tadayoshi Ohkuma / tad@omoikane.co.jp Omoikane Ltd. / http://www.omoikane.co.jp
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