Date: Thu, 25 Jul 2002 15:18:14 +0200 From: "Marco Berizzi" <pupilla@hotmail.com> To: hiten@uk.FreeBSD.org Cc: freebsd-newbies@FreeBSD.ORG Subject: Re: block device vs char device Message-ID: <LAW2-F111xOgQSCEwN10001cec8@hotmail.com>
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Hi Hiten,
Thanks for the reply about char & block devices.
Now all is much more clean.
About cd, handbook reports:
...
Suppose you add the IDE CD-ROM support to the
kernel. The line to add is:
device acd0
This means that you should look for some entries
that start with acd0 in the /dev directory, possibly
followed by a letter, such as c, or preceded by the
letter r, which means a ``raw'' device. It turns out
that those files are not there, so you must change
to the /dev directory and type:
# sh MAKEDEV acd0
When this script finishes, you will find that there
are now acd0c and racd0c entries in /dev so you know
that it executed correctly.
...
I haven't found anything about the difference
between cd0a & cd0c.
Any hints?
>From: Hiten Pandya <hitmaster2k@yahoo.com>
>Reply-To: hiten@uk.FreeBSD.org
>To: Marco Berizzi <pupilla@hotmail.com>, freebsd-newbies@FreeBSD.ORG
>Subject: Re: block device vs char device
>Date: Thu, 25 Jul 2002 05:43:00 -0700 (PDT)
>
>Hello Marco.
>
>--- Marco Berizzi <pupilla@hotmail.com> wrote:
> > [...]
> > This is the output (partial) from ls -l /dev of my
> > FreeBSD 4.6 i386 box.
> >
> > [ ... ls output snipped ]
> >
> > Why /dev/MAKEDEV create these nodes as char device? Should't
> > these device be created as block device (disk & cdrom)?
>
>OK. First of all, block device support used to exist in FreeBSD,
>till FreeBSD 4.2(or 3), and after that, the whole block device
>subsystem was replaced with a character device subsystem; this
>had its advantages. Apart from performance, I am not sure
>what other advantages it offered; but since 4.3, all device nodes
>use the Character Device Driver Interface, i.e. is why it results
>in character nodes.
>
>For the user, this should not make any difference, as it still
>offers the same functionality as it did when they were as block
>devices, unless you go far into the internals.
>
> > Other question. Which the difference between /dev/cd0a &
> > /dev/cd0c?
>
>The FreeBSD Handbook / FAQ should contain an answer for this question.
>
> > Last: majors are listed in /usr/src/sys/conf/majors
> > and minors?
>
>I am not sure about this question. sorry.
>
> -- Hiten
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