linux-kernel - Re: [PATCH v4 2/9] serdev: Add an API to find the serdev controller associated with the devicetree node

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Message-ID: <jngg3qmacno5obsz3ksaggt2pg5btrtuwjwuzrqr7x6timnm5n@ez6ta7uvql7i>
Date: Wed, 14 Jan 2026 21:30:23 +0530
From: Manivannan Sadhasivam <mani@...nel.org>
To: Hans de Goede <hansg@...nel.org>
Cc: manivannan.sadhasivam@....qualcomm.com, Rob Herring <robh@...nel.org>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Jiri Slaby <jirislaby@...nel.org>, 
	Nathan Chancellor <nathan@...nel.org>, Nicolas Schier <nicolas.schier@...ux.dev>, 
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>, Mark Pearson <mpearson-lenovo@...ebb.ca>, 
	"Derek J. Clark" <derekjohn.clark@...il.com>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
	Conor Dooley <conor+dt@...nel.org>, Marcel Holtmann <marcel@...tmann.org>, 
	Luiz Augusto von Dentz <luiz.dentz@...il.com>, Bartosz Golaszewski <brgl@...ev.pl>, 
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, Bartosz Golaszewski <brgl@...nel.org>, 
	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org, 
	platform-driver-x86@...r.kernel.org, linux-pci@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-arm-msm@...r.kernel.org, linux-bluetooth@...r.kernel.org, linux-pm@...r.kernel.org, 
	Stephan Gerhold <stephan.gerhold@...aro.org>, Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>, 
	linux-acpi@...r.kernel.org
Subject: Re: [PATCH v4 2/9] serdev: Add an API to find the serdev controller
 associated with the devicetree node

On Wed, Jan 14, 2026 at 03:01:51PM +0100, Hans de Goede wrote:
> Hi Mani,
> 
> Thank you for your work in this.
> 
> On 12-Jan-26 17:26, Manivannan Sadhasivam via B4 Relay wrote:
> > From: Manivannan Sadhasivam <manivannan.sadhasivam@....qualcomm.com>
> > 
> > Add of_find_serdev_controller_by_node() API to find the serdev controller
> > device associated with the devicetree node.
> > 
> > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@....qualcomm.com>
> > ---
> >  drivers/tty/serdev/core.c | 16 ++++++++++++++++
> >  include/linux/serdev.h    |  9 +++++++++
> >  2 files changed, 25 insertions(+)
> > 
> > diff --git a/drivers/tty/serdev/core.c b/drivers/tty/serdev/core.c
> > index b33e708cb245..25382c2d63e6 100644
> > --- a/drivers/tty/serdev/core.c
> > +++ b/drivers/tty/serdev/core.c
> > @@ -504,6 +504,22 @@ struct serdev_controller *serdev_controller_alloc(struct device *host,
> >  }
> >  EXPORT_SYMBOL_GPL(serdev_controller_alloc);
> >  
> > +/**
> > + * of_find_serdev_controller_by_node() - Find the serdev controller associated
> > + *					 with the devicetree node
> > + * @node:	Devicetree node
> > + *
> > + * Return: Pointer to the serdev controller associated with the node. NULL if
> > + * the controller is not found.
> > + */
> > +struct serdev_controller *of_find_serdev_controller_by_node(struct device_node *node)
> > +{
> > +	struct device *dev = bus_find_device_by_of_node(&serdev_bus_type, node);
> > +
> > +	return (dev && dev->type == &serdev_ctrl_type) ? to_serdev_controller(dev) : NULL;
> > +}
> > +EXPORT_SYMBOL_GPL(of_find_serdev_controller_by_node);
> > +
> 
> This new of_find_serdev_controller_by_node() function needs:
> 
> #ifdef CONFIG_OF ... #endif
> 
> around it, to match the stubbing you are doing in serdev.h
> 

Ack.

> >  static int of_serdev_register_devices(struct serdev_controller *ctrl)
> >  {
> >  	struct device_node *node;
> > diff --git a/include/linux/serdev.h b/include/linux/serdev.h
> > index ecde0ad3e248..db9bfaba0662 100644
> > --- a/include/linux/serdev.h
> > +++ b/include/linux/serdev.h
> > @@ -333,4 +333,13 @@ static inline bool serdev_acpi_get_uart_resource(struct acpi_resource *ares,
> >  }
> >  #endif /* CONFIG_ACPI */
> >  
> > +#ifdef CONFIG_OF
> > +struct serdev_controller *of_find_serdev_controller_by_node(struct device_node *node);
> > +#else
> > +struct serdev_controller *of_find_serdev_controller_by_node(struct device_node *node)
> > +{
> > +	return NULL;
> > +}
> 
> stubs like this one should be static inline to avoid warnings like this one:
> 
> In file included from drivers/tty/serdev/core.c:21:
> ./include/linux/serdev.h:339:27: warning: no previous prototype for ‘of_find_serdev_controller_by_node’ [-Wmissing-prototypes]
>   339 | struct serdev_controller *of_find_serdev_controller_by_node(struct device_node *node)
>       |                           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 

Darn... Will fix it. Thanks for spotting!

- Mani

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