On Thu, Mar 02, 2017 at 11:14:37AM -0500, Kevin O'Connor wrote: > On Wed, Mar 01, 2017 at 01:45:33PM +0300, Roman Kagan wrote: > > A number of SCSI drivers currently only see luns #0 in their targets. > > > > This may be a problem when drives have to be assigned bigger lun > > numbers, e.g. because the storage controllers don't provide enough > > target numbers to accomodate all drives. > > (In particular, I'm about to submit a driver for Hyper-V VMBus SCSI > > controller which is limited to 2 targets only). > > > > This series adds generic SCSI lun enumeration (either via REPORT LUNS > > command or sequentially trying every lun), and makes the respective > > drivers use it. > > Thanks. Let me make sure I understand this series. Some scsi > controllers have hardware specific mechanisms for finding the number > of luns (usb-msc, megasas, pvscsi) and some controllers use a generic > REPORT LUNS mechanism (virtio-scsi, esp-scsi, usb-uas, mpt-scsi, > lsi-scsi). > > The basic difficulty with implementing REPORT LUNS in seabios is that > the code needs a "struct drive_s" to issue the REPORT LUNS command, > but since the drive parameters (or even the number of drives) aren't > known, a dummy "lun0" drive_s must be created just for REPORT LUNS. > Thus the series breaks the driver xxx_add_lun() functions into > xxx_init_lun() and xxx_add_lun() so that a dummy lun0 can be created. > > An additional complexity is that the REPORT LUNS mechanism is broken > in current QEMU on lsi-scsi and mpt-scsi. > > Your goal is to add support for "Hyper-V VMBus SCSI" which also > requires REPORT LUNS. > > Is the above correct?
Absolutely. I couldn't have explained it better. One minor nit is that, strictly speaking, the upcoming vmbus scsi driver doesn't *require* REPORTS LUNS. It's just that it would be too limiting if the users had to stick with lun #0 only like was currently the case with other drivers: here the number of available targets was only 2, and thus the number of BIOS-visible disks would be no more than that. So I thought it was a good idea to start with a series that adds generic lun enumeration to the SCSI layer, that would lift this limitation for the future vmbus scsi and could benefit other drivers, too. Thanks, Roman. _______________________________________________ SeaBIOS mailing list [email protected] https://www.coreboot.org/mailman/listinfo/seabios
