Re: [PATCH] serial: fsl_lpuart: add support for GPIO-controlled modem lines

[Greg Kroah-Hartman]

On Wed, Sep 23, 2026 at 10:41:09PM +0200, João Loureiro wrote:
> On Wed, Sep 23, 2026 at 02:53PM +0200, Greg Kroah-Hartman wrote:
> > On Wed, Aug 19, 2026 at 04:44:53PM +0200, João Loureiro wrote:
> > > --- a/drivers/tty/serial/Kconfig
> > > +++ b/drivers/tty/serial/Kconfig
> > > @@ -1301,6 +1301,7 @@ config SERIAL_FSL_LPUART
> > >       tristate "Freescale lpuart serial port support"
> > >       depends on HAS_DMA
> > >       select SERIAL_CORE
> > > +     select SERIAL_MCTRL_GPIO if GPIOLIB
> >
> > Why not depends?
> 
> Because SERIAL_MCTRL_GPIO is a hidden symbol.  It is declared as a bare
> "tristate" with no prompt at the end of the same Kconfig file, so it can
> only ever be enabled by a select.  With "depends on SERIAL_MCTRL_GPIO"
> nothing could ever satisfy the dependency and SERIAL_FSL_LPUART would
> become unselectable.
> 
> The dependency is also not a hard one.  serial_mctrl_gpio.h provides
> no-op static inlines for the !CONFIG_GPIOLIB case, so fsl_lpuart still
> builds and behaves exactly as before when GPIOLIB is off; the GPIO modem
> lines are an optional extra rather than a requirement.  A depends would
> silently drop LPUART from those configurations.
> 
> Finally, this is what every other user of the helpers does:
> SERIAL_ATMEL, SERIAL_IMX, SERIAL_SH_SCI, SERIAL_STM32, SERIAL_MXS_AUART,
> SERIAL_SA1100, SERIAL_CLPS711X and SERIAL_AR933X all spell it as
> "select SERIAL_MCTRL_GPIO if GPIOLIB" in the same file, so this keeps
> fsl_lpuart consistent with them.

for some reason your first email in this thread is not on
lore.kernel.org so I can't run the CI tools on it.

Can you resend a new version so that we can test it?

thanks,

greg k-h