From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:34447) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Z8Ao8-0001wH-FF for qemu-devel@nongnu.org; Thu, 25 Jun 2015 13:19:25 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Z8Ao7-0002nJ-5V for qemu-devel@nongnu.org; Thu, 25 Jun 2015 13:19:24 -0400 Message-ID: <558C3812.7060202@redhat.com> Date: Thu, 25 Jun 2015 19:19:14 +0200 From: Laurent Vivier MIME-Version: 1.0 References: <3B3C7431-1003-4AAA-90AF-0E1A154DFBE2@gmail.com> <5589A026.5020800@redhat.com> <455CF92B-58FA-446D-9EB0-42661C23B739@gmail.com> <87pp4kxos3.fsf@blackfin.pond.sub.org> <7B989F99-B95C-4D53-AA2D-29B87634D2BB@gmail.com> <558C22BD.1020404@redhat.com> <558C2852.3050102@redhat.com> <558C295C.2030108@redhat.com> In-Reply-To: <558C295C.2030108@redhat.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] block.c: fix real cdrom detection List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini , Programmingkid , Markus Armbruster Cc: Kevin Wolf , Peter Maydell , qemu-devel qemu-devel , Qemu-block On 25/06/2015 18:16, Paolo Bonzini wrote: > > > On 25/06/2015 18:12, Laurent Vivier wrote: >> >> >> On 25/06/2015 17:48, Paolo Bonzini wrote: >>> >>> On 25/06/2015 17:32, Programmingkid wrote: >>>>> I think we are going to have to agree to disagree. I have never >>>>> used the /dev/sr(0 | 1) devices and don't see how they would be >>>>> effected by this patch. Are you trying to say the /dev/sr(0 | 1) >>>>> devices *should* be handled by this patch? >>>> >>>> Thinking about your question some more, I see what you mean. On Linux >>>> /dev/sr0 refers to the cdrom drive. Also on Linux, the /dev/cdrom >>>> link refers to the /dev/sr0 device file. So if you just use >>>> /dev/cdrom, you are good. >>> >>> Well, that's not how things work. >>> >>> If you do things like that, you end up with a bunch of hacks, not with a >>> decent piece of software. >>> >>> There is support for CD-ROM passthrough on Linux and FreeBSD in >>> block/raw-posix.c. Perhaps the FreeBSD support can be extended to OS X >>> as well. >>> >> >> In fact, programmingkid, you should fix it in hdev_open() where there is >> already a #if __APPLE__ . >> >> Paolo, I agree with you but : >> >> hdev_open() >> >> #if defined(__linux__) >> { >> char resolved_path[ MAXPATHLEN ], *temp; >> >> temp = realpath(filename, resolved_path); >> if (temp && strstart(temp, "/dev/sg", NULL)) { >> bs->sg = 1; >> } >> #endif >> >> I'm wondering who had this strange idea... :) > > I was very scared to type "git blame" here. :) But the question is also http://geek-and-poke.com/2013/11/24/simply-explained BTW, it is a legacy from 2006: 19cb373 better support of host drives coming from MacOS X (again!): 3b0d4f6 OS X: support for the built in CD-ROM drive (Mike Kronenberg) > where to put the checks. Putting it at a random place in block.c is not > a good idea. > > But yes, this is also bad. It should use stat and check the major/minor > numbers. Yes, we should check if major is SCSI_GENERIC_MAJOR (21) (on linux). We can also try to send an SG command like in cdrom_probe_device(). Something like in scsi_generic_realize(): rc = blk_ioctl(s->conf.blk, SG_GET_VERSION_NUM, &sg_version); if (rc < 0) { error_setg(errp, "cannot get SG_IO version number: %s. " "Is this a SCSI device?", strerror(-rc)); return; } Laurent