Re: [PATCH] serial: 8250: don't register ports that have no hardware

From: Lucas Tanure

Date: Wed Aug 19 2026 - 02:40:31 EST


On 19/08/2026 06:57, Greg Kroah-Hartman wrote:
On Tue, Aug 18, 2026 at 07:52:00PM +0100, Lucas Tanure wrote:
The 8250 driver creates a fixed set of port slots at boot and
registers a ttyS device for each one, even when the slot describes no
hardware. On device tree platforms those slots are empty, but they
still take the ttyS0..ttyS3 names.

New Amlogic SoCs (S4, T7) name their real UARTs ttyS as well. With
both drivers built in, as in arm64 defconfig, the real port fails to bind:

Then fix that bug, don't break everyone else's systems because of it.

Hi,

Understood. I thought preventing 8250 from probing on devices that don't use it would be a good idea, and fix my bug. Thanks for the feedback.

I will tak to Amlogic list the ttyS name collision introduced for the new Amlogic SoCs in e71aab9d6132.

Thanks,
Lucas
greg k-h