Re: [Qemu-devel] [RESEND] [PATCH] ide: fix GET_CONFIGURATION DVD-ROM support

[Carlo Marcelo Arenas Belon]

On Sat, Jan 05, 2008 at 10:28:34AM +0000, Stuart Brady wrote:
> On Fri, Jan 04, 2008 at 09:53:09PM -0600, Rob Landley wrote:
> > Except that according to http://en.wikipedia.org/wiki/CD-ROM it's actually 
> > 703 
> > and 1/8 binary megabytes (360,000 sectors *2048 bytes), which would be 
> > 1440000.
> 
> Apparently that value comes from 75 sectors per second * 80 minutes...
> 75*80*60 = 360000, and of course, 360000*2048/512 = 1440000, although
> it actually seems that it should be one sector less than 80 minutes, 
> which is 359999 2048-byte sectors or 1439996 512-byte chunks.
> 
> BTW, there are/were also 90 and 99 minute 'CD-Rs' -- Wikipedia's page on 
> CD-Rs describes them, but they were never very popular, and a lot of 
> drives can't read the discs.

the exact number of sectors is really not that relevant, as the whole point
here is to try to detect if it is a CD (700MB) or a DVD (4.7GB) and the logic
is just assuming that if it has more sectors than you should normally expect
in a CD, then it is a DVD.

attached the program I used in the guests (only works on Linux) to poke the 
emulated drive (or a physical drive if you feel like) and compare the responses
(you will need to take a look at the SPEC tables to interpret the data though)

for my own tests (using a linux guest with -cdrom /dev/cdrom in my linux
host that has a DVD-+RW drive) :

   700MB CD-R = 1374880 (with FreeSBIE 2.0.1)
  4.7GB DVD-R = 6939520 (with SXDE 9/07)

feel free to report back with the value to use then if you happen to have a CD
that is completely full but I had already enough problems trying to get this
merged without trying to change the code that much to try to guess a better
magic number than the one was originally used (I like 1440000 though)

Carlo

ide-atapi.c
Description: Text document