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Re: About /dev/sr impatience with automatic tray loading




On Monday 10 December 2018 08:58:39 Thomas Schmitt wrote:


> I wrote:
[...]
> > > I use:
> > >   xorriso -outdev /dev/sr0
> > > before trying to read the medium by POSIX i/o like dd(1) or
> > > read(2).
>
> Gene Heskett wrote:
> > This is also something that has not been installed till now, and has
> > more buttons than grandma's button jar.
>
> But you don't need K3b to get your backup stuff done.
>
> > But could it be configured into k3b for automatic usage?
>
> We would have to find out why K3b fails. Did it eject the tray and
> re-load it, before it tried to verify ?
>
yes

> If not, then it does not suffer from above kernel bug, but rather from
> something else.
>
> If the tray moved out and in, then it tries to work around the problem
> of mixing POSIX i/o with writing via ioctl(SG_IO) by the burn backend.
> Only tray loading forces the kernel to re-assess the new medium
> content. (It would only need a small change in ioctl(BLKRRPART) to let
> it re-assess the content of a /dev/sr before bailing out because there
> is no partition table supposed to be assessed on /dev/sr. Like:
>    https://www.spinics.net/lists/linux-block/msg22999.html
> )
> A workaround in K3b would be let it retry on error ENOMEDIUM for about
> 30 seconds and to only then give up.
>
That ought to be doable, but would that not delay the ready by banging on 
the drive for a status report during that time? It only has so much cpu 
power.

Some of this ready delay may be due to drives today being able to handle 
more and more disk types than the basic CD, and configuring itself to 
use the correct parameters would extend that testing phase as it finds 
the correct configuration.  That makes sense to me at least.
>
> Have a nice day :)
>
> Thomas



-- 
Cheers, Thomas, Gene Heskett
--
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