[PATCH] serial: core: Add option to enable RS485 mode via GPIO

[PATCH] serial: core: Add option to enable RS485 mode via GPIO

[Tomas Paukrt]

This patch provides an option to enable the RS485 mode at boot time
based on the state of a GPIO pin (DIP switch or configuration jumper).
The GPIO is defined by the device tree property "rs485-mode-gpio".

Signed-off-by: Tomas Paukrt <tomaspaukrt@email.cz>
---
 drivers/tty/serial/serial_core.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index f1348a5..444d7fd 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -3603,6 +3603,18 @@ int uart_get_rs485_mode(struct uart_port *port)
 	}

 	/*
+	 * Enable the RS485 mode based on the state of a GPIO pin.
+	 */
+	desc = devm_gpiod_get_optional(dev, "rs485-mode", GPIOD_IN);
+	if (IS_ERR(desc))
+		return dev_err_probe(dev, PTR_ERR(desc), "Cannot get rs485-mode-gpio\n");
+	if (desc) {
+		if (gpiod_get_value(desc))
+			rs485conf->flags |= SER_RS485_ENABLED;
+		devm_gpiod_put(dev, desc);
+	}
+
+	/*
 	 * Disabling termination by default is the safe choice:  Else if many
 	 * bus participants enable it, no communication is possible at all.
 	 * Works fine for short cables and users may enable for longer cables.
--
2.7.4

Re: [PATCH] serial: core: Add option to enable RS485 mode via GPIO

[Lino Sanfilippo]

Hi,

On 15.11.23 at 21:07, Tomas Paukrt wrote:
> This patch provides an option to enable the RS485 mode at boot time
> based on the state of a GPIO pin (DIP switch or configuration jumper).
> The GPIO is defined by the device tree property "rs485-mode-gpio".

This needs documentation in rs485.yaml.

>
> Signed-off-by: Tomas Paukrt <tomaspaukrt@email.cz>
> ---
>  drivers/tty/serial/serial_core.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
>
> diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
> index f1348a5..444d7fd 100644
> --- a/drivers/tty/serial/serial_core.c
> +++ b/drivers/tty/serial/serial_core.c
> @@ -3603,6 +3603,18 @@ int uart_get_rs485_mode(struct uart_port *port)
>  	}
>
>  	/*
> +	 * Enable the RS485 mode based on the state of a GPIO pin.
> +	 */
> +	desc = devm_gpiod_get_optional(dev, "rs485-mode", GPIOD_IN);
> +	if (IS_ERR(desc))
> +		return dev_err_probe(dev, PTR_ERR(desc), "Cannot get rs485-mode-gpio\n");
> +	if (desc) {
> +		if (gpiod_get_value(desc))
> +			rs485conf->flags |= SER_RS485_ENABLED;
> +		devm_gpiod_put(dev, desc);
> +	}

So this means RS485 cannot be disabled any more after that. Then we must not allow
to unset SER_RS485_ENABLED if userspace tries to do so via TIOCSRS485.

Regards,
Lino

Re: [PATCH v2] serial: core: Add option to enable RS485 mode via GPIO

[Tomas Paukrt]

This patch provides an option to enable the RS485 mode at boot time
based on the state of a GPIO pin (DIP switch or configuration jumper).
The GPIO is defined by the device tree property "rs485-mode-gpio".

Signed-off-by: Tomas Paukrt <tomaspaukrt@email.cz>
---
 Documentation/devicetree/bindings/serial/rs485.yaml |  4 ++++
 drivers/tty/serial/serial_core.c                    | 12 ++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/Documentation/devicetree/bindings/serial/rs485.yaml b/Documentation/devicetree/bindings/serial/rs485.yaml
index 9418fd6..7a72f37 100644
--- a/Documentation/devicetree/bindings/serial/rs485.yaml
+++ b/Documentation/devicetree/bindings/serial/rs485.yaml
@@ -47,6 +47,10 @@ properties:
       later with proper ioctl.
     $ref: /schemas/types.yaml#/definitions/flag

+  rs485-mode-gpio:
+    description: GPIO pin to enable the RS485 mode at boot time.
+    maxItems: 1
+
   rs485-rx-during-tx:
     description: enables the receiving of data even while sending data.
     $ref: /schemas/types.yaml#/definitions/flag
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index f1348a5..f1bf0b9 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -3603,6 +3603,18 @@ int uart_get_rs485_mode(struct uart_port *port)
 	}

 	/*
+	 * Enable the RS485 mode based on the state of a GPIO pin.
+	 */
+	desc = devm_gpiod_get_optional(dev, "rs485-mode", GPIOD_IN);
+	if (IS_ERR(desc))
+		return dev_err_probe(dev, PTR_ERR(desc), "Cannot get rs485-mode-gpio\n");
+	if (desc) {
+		if (gpiod_get_value(desc))
+			rs485conf->flags |= SER_RS485_ENABLED;
+		devm_gpiod_put(dev, desc);
+	}
+
+	/*
 	 * Disabling termination by default is the safe choice:  Else if many
 	 * bus participants enable it, no communication is possible at all.
 	 * Works fine for short cables and users may enable for longer cables.
--
2.7.4

Re: [PATCH v2] serial: core: Add option to enable RS485 mode via GPIO

[Krzysztof Kozlowski]

On 20/11/2023 08:55, Tomas Paukrt wrote:
> This patch provides an option to enable the RS485 mode at boot time

Please do not use "This commit/patch", but imperative mood. See longer
explanation here:
https://elixir.bootlin.com/linux/v5.17.1/source/Documentation/process/submitting-patches.rst#L95

> based on the state of a GPIO pin (DIP switch or configuration jumper).
> The GPIO is defined by the device tree property "rs485-mode-gpio".
> 
> Signed-off-by: Tomas Paukrt <tomaspaukrt@email.cz>

Please use scripts/get_maintainers.pl to get a list of necessary people
and lists to CC. It might happen, that command when run on an older
kernel, gives you outdated entries. Therefore please be sure you base
your patches on recent Linux kernel.

You missed at least devicetree list (maybe more), so this won't be
tested by automated tooling. Performing review on untested code might be
a waste of time, thus I will skip this patch entirely till you follow
the process allowing the patch to be tested.

Please kindly resend and include all necessary To/Cc entries.

> ---
>  Documentation/devicetree/bindings/serial/rs485.yaml |  4 ++++
>  drivers/tty/serial/serial_core.c                    | 12 ++++++++++++
>  2 files changed, 16 insertions(+)

Please run scripts/checkpatch.pl and fix reported warnings. Some
warnings can be ignored, but the code here looks like it needs a fix.
Feel free to get in touch if the warning is not clear.

Please use subject prefixes matching the subsystem. You can get them for
example with `git log --oneline -- DIRECTORY_OR_FILE` on the directory
your patch is touching.

Best regards,
Krzysztof

Re: [PATCH v3 1/2] serial: core: Add option to enable RS485 mode via GPIO

[Tomas Paukrt]

Add an option to enable the RS485 mode at boot time based on
the state of a GPIO pin (DIP switch or configuration jumper).
The GPIO is defined by the device tree property "rs485-mode-gpio".

Signed-off-by: Tomas Paukrt <tomaspaukrt@email.cz>
---
 drivers/tty/serial/serial_core.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index f1348a5..f1bf0b9 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -3603,6 +3603,18 @@ int uart_get_rs485_mode(struct uart_port *port)
 	}

 	/*
+	 * Enable the RS485 mode based on the state of a GPIO pin.
+	 */
+	desc = devm_gpiod_get_optional(dev, "rs485-mode", GPIOD_IN);
+	if (IS_ERR(desc))
+		return dev_err_probe(dev, PTR_ERR(desc), "Cannot get rs485-mode-gpio\n");
+	if (desc) {
+		if (gpiod_get_value(desc))
+			rs485conf->flags |= SER_RS485_ENABLED;
+		devm_gpiod_put(dev, desc);
+	}
+
+	/*
 	 * Disabling termination by default is the safe choice:  Else if many
 	 * bus participants enable it, no communication is possible at all.
 	 * Works fine for short cables and users may enable for longer cables.
--
2.7.4

Re: [PATCH v3 1/2] serial: core: Add option to enable RS485 mode via GPIO

[Krzysztof Kozlowski]

On 20/11/2023 22:45, Tomas Paukrt wrote:
> Add an option to enable the RS485 mode at boot time based on
> the state of a GPIO pin (DIP switch or configuration jumper).
> The GPIO is defined by the device tree property "rs485-mode-gpio".
> 
> Signed-off-by: Tomas Paukrt <tomaspaukrt@email.cz>
> ---
>  drivers/tty/serial/serial_core.c | 12 ++++++++++++

Why the subject is "Re:"? Please send each patchset as independent thread.

Best regards,
Krzysztof

Re: [PATCH v3 1/2] serial: core: Add option to enable RS485 mode via GPIO

[Greg Kroah-Hartman]

On Mon, Nov 20, 2023 at 10:45:20PM +0100, Tomas Paukrt wrote:
> Add an option to enable the RS485 mode at boot time based on
> the state of a GPIO pin (DIP switch or configuration jumper).
> The GPIO is defined by the device tree property "rs485-mode-gpio".
> 
> Signed-off-by: Tomas Paukrt <tomaspaukrt@email.cz>
> ---
>  drivers/tty/serial/serial_core.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
> index f1348a5..f1bf0b9 100644
> --- a/drivers/tty/serial/serial_core.c
> +++ b/drivers/tty/serial/serial_core.c
> @@ -3603,6 +3603,18 @@ int uart_get_rs485_mode(struct uart_port *port)
>  	}
> 
>  	/*
> +	 * Enable the RS485 mode based on the state of a GPIO pin.
> +	 */
> +	desc = devm_gpiod_get_optional(dev, "rs485-mode", GPIOD_IN);
> +	if (IS_ERR(desc))
> +		return dev_err_probe(dev, PTR_ERR(desc), "Cannot get rs485-mode-gpio\n");
> +	if (desc) {
> +		if (gpiod_get_value(desc))
> +			rs485conf->flags |= SER_RS485_ENABLED;
> +		devm_gpiod_put(dev, desc);
> +	}
> +
> +	/*
>  	 * Disabling termination by default is the safe choice:  Else if many
>  	 * bus participants enable it, no communication is possible at all.
>  	 * Works fine for short cables and users may enable for longer cables.
> --
> 2.7.4
> 

Hi,

This is the friendly patch-bot of Greg Kroah-Hartman.  You have sent him
a patch that has triggered this response.  He used to manually respond
to these common problems, but in order to save his sanity (he kept
writing the same thing over and over, yet to different people), I was
created.  Hopefully you will not take offence and will fix the problem
in your patch and resubmit it so that it can be accepted into the Linux
kernel tree.

You are receiving this message because of the following common error(s)
as indicated below:

- This looks like a new version of a previously submitted patch, but you
  did not list below the --- line any changes from the previous version.
  Please read the section entitled "The canonical patch format" in the
  kernel file, Documentation/process/submitting-patches.rst for what
  needs to be done here to properly describe this.

If you wish to discuss this problem further, or you have questions about
how to resolve this issue, please feel free to respond to this email and
Greg will reply once he has dug out from the pending patches received
from other developers.

thanks,

greg k-h's patch email bot

Re: [PATCH v3 2/2] dt-bindings: serial: Add option to enable RS485 mode via GPIO

[Tomas Paukrt]

Add the device tree property "rs485-mode-gpio".

Signed-off-by: Tomas Paukrt <tomaspaukrt@email.cz>
---
 Documentation/devicetree/bindings/serial/rs485.yaml | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Documentation/devicetree/bindings/serial/rs485.yaml b/Documentation/devicetree/bindings/serial/rs485.yaml
index 9418fd6..7a72f37 100644
--- a/Documentation/devicetree/bindings/serial/rs485.yaml
+++ b/Documentation/devicetree/bindings/serial/rs485.yaml
@@ -47,6 +47,10 @@ properties:
       later with proper ioctl.
     $ref: /schemas/types.yaml#/definitions/flag

+  rs485-mode-gpio:
+    description: GPIO pin to enable RS485 mode at boot time.
+    maxItems: 1
+
   rs485-rx-during-tx:
     description: enables the receiving of data even while sending data.
     $ref: /schemas/types.yaml#/definitions/flag
--
2.7.4

Re: [PATCH v3 2/2] dt-bindings: serial: Add option to enable RS485 mode via GPIO

[Krzysztof Kozlowski]

On 20/11/2023 22:45, Tomas Paukrt wrote:
> Add the device tree property "rs485-mode-gpio".
> 
> Signed-off-by: Tomas Paukrt <tomaspaukrt@email.cz>
> ---
>  Documentation/devicetree/bindings/serial/rs485.yaml | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/serial/rs485.yaml b/Documentation/devicetree/bindings/serial/rs485.yaml
> index 9418fd6..7a72f37 100644
> --- a/Documentation/devicetree/bindings/serial/rs485.yaml
> +++ b/Documentation/devicetree/bindings/serial/rs485.yaml
> @@ -47,6 +47,10 @@ properties:
>        later with proper ioctl.
>      $ref: /schemas/types.yaml#/definitions/flag
>  
> +  rs485-mode-gpio:
> +    description: GPIO pin to enable RS485 mode at boot time.
> +    maxItems: 1
> +

This does not look like generic RS485 property. Commit msg also does not
help to understand the context.

Best regards,
Krzysztof