Re: wrong number of serial port detected

["Jason Dravet" <dravet@hotmail.com>]

> From: Russell King <rmk+lkml@arm.linux.org.uk>
> To: Jason Dravet <dravet@hotmail.com>
> CC: linux-kernel@vger.kernel.org
> Subject: Re: wrong number of serial port detected
> Date: Wed, 7 Dec 2005 21:15:51 +0000
>
> On Wed, Dec 07, 2005 at 01:59:43PM -0600, Jason Dravet wrote:
> > >From: Russell King <rmk+lkml@arm.linux.org.uk>
> > >To: Jason Dravet <dravet@hotmail.com>
> > >CC: linux-kernel@vger.kernel.org
> > >Subject: Re: wrong number of serial port detected
> > >Date: Wed, 7 Dec 2005 15:50:34 +0000
> > >
> > >On Wed, Dec 07, 2005 at 09:44:29AM -0600, Jason Dravet wrote:
> > >> So I ask this mailing list Can the kernel detect the proper number of
> > >> serial ports or not?
> > >
> > >It does detect serial ports found in the machine.
> > >
> > >However, it _always_ offers the configured number of serial devices.
> > >This is to allow folk whose ports are not autodetected to configure
> > >them appropriately via the setserial command.  If they were not
> > >available, they could not configure them.
> > >
> > Then may I ask how XP does it?  I have to dual boot between XP and 
> Fedora.
> > When I go into XP's device manager I see all of the appropriate hardware
> > listed, no extra serial ports.  When I boot into Fedora and go into 
> /dev, I
> > see the same hardware except I have 32 serial ports and 64 tty nodes 
> (tty
> > is for virtual terminals right?).  How can 1 OS show the correct number 
> and
> > another show the wrong number?  I ask so I can better understand what is
> > going on.
>
> It seems you are comparing apples (XP's device manager) with oranges
> (/dev directory).  They're two entirely different things.
>
> The former lists devices which _are_ present in your system.
>
> The latter provides the filesystem namespace for applications to access
> devices which may or may not be present in your system.
I thought the purpose of udev was to create device manager like 
functionality.  I posted my question here because udev is creating 32 nodes. 
 Udev gets that information from the kernel serial port driver.  Thanks to 
your explanation I now understand.  This is why I ask questions so I can 
learn.

> As for your 64 VT tty device nodes - these "devices" are created
> dynamically when the device node is opened.  The act of opening the
> device node is defined to be the creation event.  If the device node
> did not exist, there would be no way to create _any_ virtual terminals.
I thought there were only 7 tty devices (Ctrl-F1 to Ctrl-F7) for local 
system login?  Ctrl-F7 being for Xwindows.  Did I miss something?

Thank you for taking the time to answer my questions.  I really appreciate 
it.
Jason


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