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From: steve@wlbreng1.UUCP (Steve Childress)
Newsgroups: comp.sys.amiga
Subject: Re: Help w/Disked for hard disks
Message-ID: <169@wlbreng1.UUCP>
Date: Thu, 22-Jan-87 11:32:05 EST
Article-I.D.: wlbreng1.169
Posted: Thu Jan 22 11:32:05 1987
Date-Received: Fri, 23-Jan-87 07:28:18 EST
References: <159@wlbreng1.UUCP> <11186@sun.uucp> <163@wlbreng1.UUCP> <11655@sun.uucp>
Reply-To: steve@wlbreng1.UUCP (0000-Steve Childress)
Organization: Eaton Inc. IMSD, Westlake Village, CA
Lines: 53

In article <11655@sun.uucp> cmcmanis@sun.uucp (Chuck McManis) writes:
>In article <163@wlbreng1.UUCP>, steve@wlbreng1.UUCP (Steve Childress) writes:
>*> Could someone explain what is meant by "DISKENV"? As far as I have read
>*> and understand, to find the in-memory rendition of the data found for
>*> mounted disks, I must write a routine to chase the list of devices looking
>*> for those associated with my driver (using my driver's ASCII name) and
>*> the look for the desired sub unit by somehow knowing its ASCII name too.
>*> 
>*> I don't know how to do the latter. Sure would like to add code to my
>*> driver so's it could automatically discover the extents of the disk
>*> partition for any arbitrary subunit. Also-- still looking to learn what
>*> is passed in D0 to the driver OPENDEVICE routine.
>*> 
>*> 		Steve Childress
>
>DISKENV is an array of longwords that describes your disk layout. It
>contains such interesting things as the number of sectors per track,
>the starting cylinder number, the ending cylinder number, the number
>of heads, etc. All of the entries are documented in the include
>file "libraries/filehandler.h". As it turns out the handler task that
>is talking to your device automatically adds in the offset to the
>first cylinder when you try to read or write file data, however if
>you are using the Exec I/O calls (DoIO, SendIO, etc) then you will
>have to add in this offset yourself. Chasing the device names is
>fairly simple, although it might be easier to store a pointer to
>your device node at startup time (when you are loaded). Currently,
>as far as I can tell the default behaviour of ADOS is to insert
>new devices at the head of the DeviceList, thus when you are 
>started your device node will be pointed to by the DeviceList pointers
>in the RootNode (I think it is called DevInfo) Also the AddDevice
>calls requires an address to a DeviceNode structure so assuming
>your driver built its device node structure then it knows where
>it is. 
>
>As it turns out there is also a Unit subfield in the DISKENV array
>and that is what I pass to the OpenDevice call in D0. 
>
>Final comment is why does your driver care how the disk is partitioned?
>Since the file handler takes care of that stuff for you? 
>
>-- 
>--Chuck McManis
>uucp: {anywhere}!sun!cmcmanis   BIX: cmcmanis  ARPAnet: cmcmanis@sun.com

In my driver, I want to access the info in mountlist so I can decide which
physical drive is being opened. My system, like many, has multiple hard disks,
and sometimes they differ in I/O techniques, e.g., stepping rate on the
head positioner. My old Tandon lacks buffered seek so whenever I change drives
I have to do a seek with a different stepping rate. Also, there is a driver
call "tell number of cylinders" or some such which requires access to this
sort of data, and it should not be hard coded.

I'll study that .h file -- thanx.