From: Jens Axboe <jens.axboe@xxxxxxxxxx> Subject: Re: block/bsg.c Date: Tue, 17 Jul 2007 08:38:11 +0200 > > As a reader of this code I'm wondering "hm, why is > > BSG_SUB_PROTOCOL_SCSI_CMD unprivileged, while other modes require > > CAP_SYS_RAWIO"?. > > > > This design/policy decision maybe was discussed on a mailing list > > somewhere, or even perhaps in a changelog (although I can't find it). But > > it is so important, and is so unobvious from a reading of the code that I'd > > suggest that it is worth some discussion right here, in a code comment. > > > It's not unprivileged, it goes through the blk_verify_command() check > list. SCSI commands goes to blk_verify_command() like SG v3 (block/scsi_ioctl.c and drivers/scsi/sg.c). Except for SCSI commands, only SAS Management Protocol (SMP) is supported now. Sending management requests needs CAP_SYS_RAWIO, that's a reasonable policy, I guess. > > And `struct sg_io_v4' has just become part of the kernel ABI? Beware that > > there is a move afoot to require test code, manpages and even LTP testcases > > for new ABI extensions. Is this interface documented anywhere? > > The documentation is likely very scarce atm, if anything. The command > layout was discussed at the storage summit and on linux-scsi. Not the latest, but Doug's RFC: http://lwn.net/Articles/208082/ gives pretty good information. > > Would I be correct in assuming that it offers services to device drivers, > > which have yet to be hooked up? > > Yes. As mentioned many lines up, it is a SCSI generic type driver that > uses the (now) defined version 4 command structure. So it'll get hooked > up to ny capable device. The SAS transport class use bsg to handle SAS Management Protocol. Every SAS object (host, device, expander, etc) has the own bsg device. They call bsg_register_queue() for the own request queue. Users can send SMP requests to any object via its bsg device. http://marc.info/?l=linux-scsi&m=118395317724148&w=2 I guess that James plan to put SMP patches in the second SCSI merge for 2.6.22. - To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
