Hi Johan,

On Thu, Sep 16, 2021 at 10:46 AM Johan Hovold [off-list ref] wrote:

On Wed, Sep 15, 2021 at 02:56:52PM +0200, Geert Uytterhoeven wrote:

quoted

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_TEST now
enables this driver.

Fix this by making SERIAL_8250_FSL visible.  Tighten the dependencies to
prevent asking the user about this driver when configuring a kernel
without appropriate Freescale SoC or ACPI support.

This tightening is arguable a separate change which risk introducing
regressions if you get it wrong and should go in a separate patch at
least.

Getting it wrong would indeed be a regression, but not tightening
that at the same time would mean I have to send a separate patch with
a Fixes tag referring to this fix, following this template:

    foo should depend on bar

    The foo hardware is only present on bar SoCs.  Hence add a
    dependency on bar, to prevent asking the user about this driver
    when configuring a kernel without bar support.

quoted

Fixes: b1442c55ce8977aa ("serial: 8250: extend compile-test coverage")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
Yes, it's ugly, but I see no better solution. Do you?

 drivers/tty/serial/8250/Kconfig | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/8250/Kconfig b/drivers/tty/serial/8250/Kconfig
index 808268edd2e82a45..a2978b31144e94f2 100644
--- a/drivers/tty/serial/8250/Kconfig
+++ b/drivers/tty/serial/8250/Kconfig

@@ -361,9 +361,13 @@ 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
+     depends on FSL_SOC || ARCH_LAYERSCAPE || SOC_LS1021A || (ARM64 && ACPI) || COMPILE_TEST
+     default FSL_SOC || ARCH_LAYERSCAPE || SOC_LS1021A || (ARM64 && ACPI)

I'd suggest just doing

        bool "Freescale 16550-style UART support (8250 based driver)"
        depends on SERIAL_8250_CONSOLE
        default PPC || ARM || ARM64

Since neither of the symbols you add to that "depends on" line is an
actual build or runtime dependency.

They are.

Then you can refine the "default" line in a follow up (or argue why you
think there should be a "depends on FSL_SOC || ...").

quoted

+     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"

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds