Date: Tue, 6 Jul 1999 21:39:53 -0600 (MDT) From: "Kenneth D. Merry" <ken@plutotech.com> To: ohashi@mickey.ai.kyutech.ac.jp (Takeshi OHASHI) Cc: garbanzo@hooked.net, dmiller@search.sparks.net, akiyama@kme.mei.co.jp, freebsd-hackers@FreeBSD.ORG Subject: Re: DVD-ram Message-ID: <199907070339.VAA88466@panzer.kdm.org> In-Reply-To: <199907070246.LAA01724@atohasi.mickey.ai.kyutech.ac.jp> from Takeshi OHASHI at "Jul 7, 1999 11:46:59 am"
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Takeshi OHASHI wrote... > ken>>Alex Zepeda wrote... > ken>>> On Tue, 6 Jul 1999, Kenneth D. Merry wrote: > ken>>> > ken>>> > IMO, DVD drives are probably best handled through the CD driver, and > ken>>> > Optical drives are probably best handled through the DA driver. The > ken>>> > CD driver doesn't currently handle writes, but it's a one-line fix to > ken>>> > change that. > ken>>> > ken>>> >From what I can tell, some of the DVD-RAM drives are actually treated as > ken>>> disks (would use the da driver). For example, check out > ken>>> http://mpeg.openprojects.net/panasonic.html to see the Linux "driver" for > ken>>> the Panasonic LF-D100. The comments outnumber the code. > ken>> > ken>>Well, that makes sense from one perspective, and doesn't make sense from > ken>>another perspective. > ken>> > ken>>Sure, DVD drives look like a disk from the standpoint that you can use > ken>>standard read *and* write calls on them. > ken>> > ken>>But in most other ways, they're like CDROM drives. You can play audio CDs > ken>>in them, mount regular data CDs in them, etc. With a disk driver, you > ken>>don't have any of the special ioctl set to deal with CD-type drives and > ken>>media. > ken>> > ken>>In fact, you probably wouldn't be able to mount disk with an ISO 9660 > ken>>filesystem using the da driver, since it doesn't support the TOC ioctls > ken>>that the cd9660 filesystem code uses. (because DA devices don't support > ken>>those SCSI commands) > ken>> > ken>>The best of both worlds for accessing a DVD-RAM drive would be to just add > ken>>write support to the CD driver. The CAM CD driver already has write > ken>>support, but it isn't currently enabled. > ken>> > ken>>The attached one-line patch enables write support, and should make things > ken>>just work. If anyone has a DVD-RAM drive and cares to test it, I'd be very > ken>>interested to hear how things work. > ken>> > ken>>Ken > ken>>-- > ken>>Kenneth Merry > ken>>ken@plutotech.com > > How do you think about some MO(Magneto Otpical disk) and PD drives? > > 3.5" 650MB and 1.3GB MO drives should handle 512KB/sector(128MB, > 230MB, 540MB) and 2048KB/sector media(640MB, 1.3GB). The CAM DA driver was specifically designed to handle various sector sizes, and should work fine with non-512 byte sector sizes. If it doesn't, it needs to be fixed. > Some PD drives use 2 LUNs. One of them is used for CD drive mode and > another is for PD drive. I don't know very much about PD drives. Can you give me a brief description of the sort of interface they present? Is it like a MO drive, or something else? What SCSI type does the PD drive LUN probe as? Optical, direct access, CDROM, what? > How do you treat write protection? DVD-RAM type II media can be remove > from the cartridge and be read as like as DVD-ROM media by some latest > DVD-ROM drives, for example Panasonic's. But the striped DVD-RAM media > is treat ad read only media by DVD-RAM drive. If the drive treats the media as read-only, then the driver will just return an error if the user tries to write to it. > In addition, there are many bugy MO drives, ex. cash probelem, and > media, ex. formated media for Windows. They cause to need some extra > error handling. Device specific error handling should be doable within the current DA driver with quirk entries. How broken are the drives in question? Can you make source code to the OD driver available, so I can take a look at it, and see what sorts of things you have to do to make these drives work? > We were very happy to use DVD-RAM/MO/PD drives on FreeBSD-2.2.X, > because pre-CAM SCSI system had the od-driver. We could not use these > devices on FreeBSD-3.X without the new od-driver. Well...I would expect that DVD-RAM drives might not work exactly as you expect, without a tweak to the CDROM driver to allow it to write to the media. MO drives should work okay with the DA driver, and since I'm not sure what PD drives look/act like, I can't really say whether they should work or not. > Thank you very much, Mr. Akiyama. Thanks for the response. I'd certainly like to hear more about the OD driver. Ken -- Kenneth Merry ken@plutotech.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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