Re: [PATCH]trivial: add CDC_RAM to ide-cd capabilities mask

[Jens Axboe <axboe@suse.de>]

On Wed, Jan 11 2006, Andrey Borzenkov wrote:
> 
> 
> -----Original Message-----
> From: Jens Axboe <axboe@suse.de>
> To: Andrey Borzenkov <arvidjaar@mail.ru>
> Date: Wed, 11 Jan 2006 10:29:38 +0100
> Subject: Re: [PATCH]trivial: add CDC_RAM to ide-cd capabilities mask
> 
> > 
> > On Wed, Jan 11 2006, Andrey Borzenkov wrote:
> > > 
> > > 
> > > > drive name:             sr0
> > > > drive speed:            1
> > > > drive # of slots:       1
> > > > Can close tray:         1
> > > > Can open tray:          1
> > > > Can lock tray:          1
> > > > Can change speed:       0
> > > > Can select disk:        0
> > > > Can read multisession:  1
> > > > Can read MCN:           1
> > > > Reports media changed:  1
> > > > Can play audio:         1
> > > > Can write CD-R:         0
> > > > Can write CD-RW:        0
> > > > Can read DVD:           0
> > > > Can write DVD-R:        0
> > > > Can write DVD-RAM:      0
> > > > Can read MRW:           1
> > > > Can write MRW:          1
> > > > Can write RAM:          1
> > > > 
> > > > There's no way this drive knows anything about MRW or random-access writing:
> > > > 
> > > ...
> > > > And an ATAPI DVD-ROM also reports (before the above patch):
> > > > 
> > > > Can read MRW:           1
> > > > Can write MRW:          1
> > > > Can write RAM:          1
> > > > 
> > > 
> > > I know. There were patches from Jens for both 2.4 and 2.6 that add MRW
> > > support to ide-cd for sure; may be for sr too, am not sure. Jens, any
> > > reasons for them not in mainstream? Otherwise probably ide-cd and sr should
> > > not announce MRW capabiliies at all, it is too confusing; I'll send a patch
> > > when I am at home.
> > 
> > MRW support is in 2.6 since ages. The MRW flag is only detected on open,
> > so it should disappear from the proc file once you have opened the
> > drive. It has to be done that way, I'm afraid.
> > 
> 
> I see, it is in generic cdrom code, sorry.
> 
> is it possible that drive supports MRW_W without supporting any other write
> method (_R/_RW)? Should not ide-cd/sr - or possibly even cdrom - mask MRW_W
> if they do not support writing at all?

I don't know why anyone would make such a device, but of course it's
possible. Masking MRW if the device can't write sounds like a safe
enough bet, I'll take a patch :)

-- 
Jens Axboe