Messages in this thread | | | Date | Mon, 6 Jan 2003 18:13:55 -0800 | From | Patrick Mansfield <> | Subject | Re: IDs |
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Andries -
On Tue, Jan 07, 2003 at 01:00:47AM +0100, Andries.Brouwer@cwi.nl wrote:
> Maybe I should ask you to explain more in detail what purpose > you have in mind. If I read your code and hear you talking > it sounds like you would like to have a string identifying > the device. But in many cases no such string exists.
Yes, but where one exists we can use it. Any recent SCSI disk should end up with a unique value in (what is currently) sdev->name. We can tell if the id sdev->name should be unique by looking at the first byte (it is not unique if the value is 'Z', SCSI_UID_UNKNOWN).
> Moreover, what precisely is "the device"? > If I have a Compact Flash card reader and read CF cards, > is the device the reader? Or the card? Or the combination? > If I have an Imation FlashGo! reader, and insert a SmartMedia > adapter, and read a SmartMedia card, is the device the reader, > the reader plus adapter, the card?
The scsi_device, whatever it represents. For removable media, we should either make sure sdev->name has a value for this storage such that we know the id is not unique, or we should check (and export to sysfs) the sdev->removable flag. I haven't checked what currently gets put into sdev->name for CF cards (or even if removable is properly set).
> If the device is the reader, then it will have a different size, > partitioning and contents each time we see it. > If the device is the card, then we need a different driver > each time we see it. > > What do you want to recognize with this ID, and why? >
For use with device naming/persistence.
For devices with a unique ID, we can always give them the same name; non-unique ID's can be named based on their location (host/channel/target/lun).
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