[PATCH v2] drivers: serial: Make sure we really return a serial device

Simon Glass sjg at chromium.org
Sun Mar 6 04:07:54 CET 2022

On Mon, 21 Feb 2022 at 14:17, Mark Kettenis <kettenis at openbsd.org> wrote:
> The stdout-path property in the device tree does not necessarily
> point at a serial device. On machines such as the Apple M1 laptops
> where the serial port isn't easy to access and users expect to see
> console output on the integrated display stdout-path may point at
> the device tree node for the framebuffer for example.
> If stdout-path does not point at a node for a serial device, the
> serial_check_stdout() will not find a bound device and will drop
> down into code that attempts to use lists_bind_fdt() to bind a
> device anyway. However, that fallback code does not check that
> the uclass of the device is UCLASS_SERIAL. So if stdout-path points
> at the framebuffer instead of the serial device it will return a
> UCLASS_VIDEO device. Since the code that calls this function
> expects the returned device to be a UCLASS_SERIAL device, U-Boot
> will crash as soon as it attempts to send output to the console.
> Add a check here to verify that the uclass of the bound device
> really is UCLASS_SERIAL. If it isn't, serial_check_stdout() will
> return an error and serial_find_console_or_panic() will use the
> serial device with sequence number 0 as the console and all is fine.
> Signed-off-by: Mark Kettenis <kettenis at openbsd.org>
> ---
> ChangeLog:
> v2: - Expand commit message
>  drivers/serial/serial-uclass.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)

Reviewed-by: Simon Glass <sjg at chromium.org>

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