Re: what binds to port
On Mon 02 Aug 2021 at 13:21:22 +0200, Thomas Schmitt wrote:
> Hi,
>
> Brian wrote:
> > Isn't /dev/sg0 the block device?
>
> /dev/sgX are character devices.
>
> https://tldp.org/HOWTO/SCSI-Generic-HOWTO/intro.html
> says
> "The driver's purpose is to allow SCSI commands to be sent directly to
> SCSI devices. [...] Various specialized applications for writing
> CD-Rs and document scanning use the sg driver."
>
> This is still the case for optical drives (sr) and hard discs (sd) which get
> an sg device file additionaly to their block device file. But it seems that
> the statement about "document scanning" could need an update.
>
>
> The main call for sg devices is ioclt(SG_IO) which performs a single SCSI
> command transaction.
> Since about 15 years it is possible to use it directly with a /dev/srX
> device file. But a bug introduced in a late version of kernel 2.6 prevented
> concurrent use of SG_IO on multiple sr devices. This ended with
> https://github.com/torvalds/linux/commit/51a8588
> which i assume went into kernel version 5.6.
> So with the currently released Debian versions, /dev/sgX is still of use
> if there is more than one sr device.
I misread sr0 as sg0; sorry to have put you to the trouble of posting.
On the bright side, you have helped clear up a misconception of mine.
--
Brian.
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