Date: Fri, 19 Jun 1998 14:42:45 -0300 (EST) From: Joao Carlos Mendes Luis <jonny@jonny.eng.br> To: ken@plutotech.com (Kenneth D. Merry) Cc: mjacob@feral.com, julian@whistle.com, ken@plutotech.com, jonny@jonny.eng.br, ckempf@enigami.com, freebsd-scsi@FreeBSD.ORG Subject: Re: Rolling CAM in, what is still needed? Message-ID: <199806191742.OAA02683@roma.coe.ufrj.br> In-Reply-To: <199806191730.LAA12458@panzer.plutotech.com> from "Kenneth D. Merry" at "Jun 19, 98 11:30:01 am"
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#define quoting(Kenneth D. Merry) // - the problem is that with the old SCSI code, to send SCSI commands // directly to a device, you opened the device itself (/dev/rcd0a or // whatever) and did the SCIOCCOMMAND ioctl on that device. CAM does // things differently, primarily because users may want to send // commands to device, even though the device's open() routine may // fail. For instance, you can't open a CD device if there is no // media inserted. But the user may want to send an INQUIRY command // to the drive, whether or not there's a CD in the drive. So, to // solve this, you have two choices: (that I can think of offhand) // - have a special control minor number for each device, and // have the open call ignore failures in read capacity, test // unit ready, etc. // - have a separate passthrough driver that doesn't have to // have any commands succeed to attach or open. Isn't this what /dev/xxx.ctl does ? // For CAM, we chose the latter. Anyway, I've gotta go, so I'll // just say that in order to have devices respond to the // SCIOCCOMMAND ioctl in the same way, we'd have to wire code to // handle that ioctl into each device driver's ioctl routine. // (probably in cam_periph_ioctl()) // // I'd rather not kludge any of this up, though, unless someone can // make a compelling case that it needs to be done. Maybe it's not a big problem, considering the ports collection. :) For me, the most important is to have the rules clearly defined. Being said that, both options are good enough. Jonny -- Joao Carlos Mendes Luis M.Sc. Student jonny@jonny.eng.br Universidade Federal do Rio de Janeiro To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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