Messages in this thread | | | Date | Fri, 3 Sep 1999 16:51:18 -0700 | From | Brian Swetland <> | Subject | Re: scsi, round robin && mailbox ? |
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[Mathieu Arnold <arn_mat@club-internet.fr>] > > and i do not see what round robin means in this context. > and the same for multiple mailboxes, i edited drivers/scsi/BusLogic.c but it's > not explained there, i also looked into Documentation/IO-mapping.txt but i > still do not understand what a mailbox really is.
The Buslogic SCSI controllers use a shared memory area for incoming and outgoing mailboxes. To enqueue a request you fill out a data structure describing the request, write its physical address into the next available outgoing mailbox, and write a "you have mail" byte to the command register. When you receive an interrupt from a Buslogic card, you scan forward in the inbound mailboxes for pointers to completed requests. Round Robin is probably in reference to one of the card's modes for scanning for new "mail". It makes things simpler in that the card just scans forward from the next available mailbox instead of checking all of them.
Brian
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