Re: [PATCH v2 1/2] serial: 8250: SERIAL_8250_FSL should not default to y when compile-testing

[Johan Hovold <johan@kernel.org>]

On Fri, Sep 24, 2021 at 09:12:30AM +0200, Geert Uytterhoeven wrote:
> Commit b1442c55ce8977aa ("serial: 8250: extend compile-test coverage")
> added compile-test support to the Freescale 16550 driver.  However, as
> SERIAL_8250_FSL is an invisible symbol, merely enabling compile-testing
> now enables this driver.
> 
> Fix this by dropping the COMPILE_TEST default again, but making the
> SERIAL_8250_FSL symbol visible instead.
> 
> Fixes: b1442c55ce8977aa ("serial: 8250: extend compile-test coverage")
> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
> ---
> v2:
>   - Split in two parts.

I realised that we can do better than this. I've prepared a patch that
preserves the old behaviour of always enabling the option on platforms
that may need it while also not enabling it by default when compile
testing.

Note that SERIAL_8250_FSL only enables a workaround for an erratum in
the Freescale UARTs in the 8250 driver (leaving the later added ACPI
support aside) and we shouldn't make it easier to disable it by mistake.

> ---
>  drivers/tty/serial/8250/Kconfig | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/tty/serial/8250/Kconfig b/drivers/tty/serial/8250/Kconfig
> index 808268edd2e82a45..0af96f3adab517f6 100644
> --- a/drivers/tty/serial/8250/Kconfig
> +++ b/drivers/tty/serial/8250/Kconfig
> @@ -361,9 +361,12 @@ config SERIAL_8250_BCM2835AUX
>  	  If unsure, say N.
>  
>  config SERIAL_8250_FSL
> -	bool
> +	bool "Freescale 16550-style UART support (8250 based driver)"
>  	depends on SERIAL_8250_CONSOLE
> -	default PPC || ARM || ARM64 || COMPILE_TEST
> +	default PPC || ARM || ARM64
> +	help
> +	  Selecting this option will add support for the 16550-style serial
> +	  port hardware found on Freescale SoCs.
>  
>  config SERIAL_8250_DW
>  	tristate "Support for Synopsys DesignWare 8250 quirks"

Johan