On Tue, Jan 27, 2009 at 12:51:25PM -0800, Sarah Sharp wrote: > On Mon, Jan 26, 2009 at 02:40:55PM -0800, Matthew Dharm wrote: > > On Mon, Jan 26, 2009 at 01:43:09PM -0800, Sarah Sharp wrote: > > > A more important question is will the SCSI layer can support command queueing > > > to the USB MSD driver, or will there need to be changes there also? > > > > Well, this is an easy question: It's supported. SCSI core supports command > > queueing. Right now, the usb-storage driver has a queue depth of 1. But, > > SCSI core will queue multiple commands to an HCD driver (the HCD set the > > queue depth limit). > > How does the host controller driver (HCD) get involved here? I haven't seen > anything like this while writing the xHCI driver. Did you mean mass storage > device (MSD) driver? Can you point me to the code that does this? Sorry, HCD (aka Host Controller Driver) is also the term used for the driver for SCSI HBAs (Host Board Adaptors). You're correct; it's not in the xHCI, it would be in MSD. Right now, since MSD only supports a queue depth of 1, there is only one "command slot" (the srb field of the datastructure). The queue depth is set in the host template in one of the scsiglue files. Matt -- Matthew Dharm Home: mdharm-usb@xxxxxxxxxxxxxxxxxx Maintainer, Linux USB Mass Storage Driver I want my GPFs!!! -- Stef User Friendly, 11/9/1998
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