Re: Christmas list for the kernel

Russell King
2005-11-23T15:37:05Z

On Wed, Nov 23, 2005 at 10:31:15AM -0500, Jon Smirl wrote:
> On 11/23/05, Russell King <rmk+lkml@arm.linux.org.uk> wrote:
> > > This is confusing...
> > >
> > > Serial: 8250/16550 driver $Revision: 1.90 $ 4 ports, IRQ sharing disabled
> > > serial8250: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
> > > serial8250: ttyS1 at I/O 0x2f8 (irq = 3) is a 16550A
> > > serial8250: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
> > > serial8250: ttyS1 at I/O 0x2f8 (irq = 3) is a 16550A
>
> Could this be the source of the four port versus the two port
> confusion in the higher layers? It says 4 ports and list four ports,
> but two are duplicates.

Only if something's parsing the kernel messages.

The "4 ports" is about the _maximum_ number of ports that the driver
will support, and it will therefore create tty devices for ttyS0 to
ttyS3 regardless of whether the hardware exists.

To see why this is done, read my previous mails in this thread.

--
Russell King
Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/
maintainer of: 2.6 Serial core