Re: mpt Serious performance issues

[Martin Husemann <martin%duskware.de@localhost>]

On Fri, Jan 28, 2011 at 11:30:16AM +0100, Stephan wrote:
> The discovery code you spoke from is part of every device driver,
> isnt`t it? The scsipi man page tells about a XS_CTL_DISCOVERY flag in
> xs_control, which i can?t find in the mpt driver. So how does e.g. the
> mpt driver tell the scsipi layer what capabilities a given device has?

It doesn't, the scsipi layer scans the bus for devices and if it finds
some it queries their mode pages (depending on supported scsi version)
and sets the ability flags.

See scsiconf.c:scsi_probe_device for details:

        /*
         * Determine the operating mode capabilities of the device.
         */
        if (periph->periph_version >= 2) {
                if ((inqbuf.flags3 & SID_CmdQue) != 0 &&
                    (quirks & PQUIRK_NOTAG) == 0)
                        periph->periph_cap |= PERIPH_CAP_TQING;
                if ((inqbuf.flags3 & SID_Linked) != 0)
                        periph->periph_cap |= PERIPH_CAP_LINKCMDS;
...

Martin