Date: Mon, 15 Oct 2012 08:27:23 +0530 From: Jack <jacks.1785@gmail.com> To: freebsd-scsi@freebsd.org Subject: Re: passstart() and immediate CCBs Message-ID: <CACmXQA3DxafwiCp4CzaFvxnvOG4=yqj0aVmODDTb8gV0jXEknw@mail.gmail.com> In-Reply-To: <20121012223203.GA68975@nargothrond.kdm.org> References: <CACmXQA141ZTRDd7DxfM41hd4idDg_uQ7%2BsWc4cZ8E%2B3aLoDJRg@mail.gmail.com> <20121012223203.GA68975@nargothrond.kdm.org>
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On Sat, Oct 13, 2012 at 4:02 AM, Kenneth D. Merry <ken@freebsd.org> wrote: > Immediate CCBs are complete when xpt_action() returns, so no callback is > needed. > Does Immediate CCB transaction is similar to polling? I mean xpt_action() is called, xfer is done and then HBA asserts interrupt, the control is transfered back to xpt_action(), then it returns. Then what is the purpose of cam_periph_ccbwait(), inside cam_periph_runccb(), just after xpt_action(). > > Immediate CCBs never go down to the hardware. The priority mechanism is > used to help determine who gets queue slots, and those are only > needed for queued CCBs. > queued CCBs means non-immediate CCBs. right? Sorry, I didn't get what do you mean by: " Immediate CCBs never go down to the hardware." I guess immediate CCBs are preferred over non-immediate CCBs, in the sense that they bypass struct cam_ed queue completely, and directly sent to HBA driver, via xpt_action(). Is it? Regards -- Jack
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