diff mbox series

[v2,1/9] serial: core: only get RS485 termination GPIO if supported

Message ID 20220703170039.2058202-2-LinoSanfilippo@gmx.de
State New
Headers show
Series [v2,1/9] serial: core: only get RS485 termination GPIO if supported | expand

Commit Message

Lino Sanfilippo July 3, 2022, 5 p.m. UTC
From: Lino Sanfilippo <l.sanfilippo@kunbus.com>

In uart_get_rs485_mode() only try to get a termination GPIO if RS485 bus
termination is supported by the driver. This prevents from allocating
and holding a GPIO descriptor for the drivers lifetimg that will never be
used.

Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
---

NOTE: 
This patch follows the design decision that "rs485_supported" is
set by the driver at initialization and cannot be modified
afterwards. However the better approach would be to let the serial
core modify the termination GPIO support setting based on the
existence of a termination GPIO. If "rs485_supported" is not a 
read-only value any more in future the logic implemented in this
patch should be adjusted accordingly.

 drivers/tty/serial/serial_core.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

Comments

Andy Shevchenko July 3, 2022, 6:27 p.m. UTC | #1
On Sun, Jul 3, 2022 at 7:02 PM Lino Sanfilippo <LinoSanfilippo@gmx.de> wrote:
>
> From: Lino Sanfilippo <l.sanfilippo@kunbus.com>
>
> In uart_get_rs485_mode() only try to get a termination GPIO if RS485 bus
> termination is supported by the driver. This prevents from allocating
> and holding a GPIO descriptor for the drivers lifetimg that will never be

lifetiming

> used.

...

>         port->rs485_term_gpio = devm_gpiod_get_optional(dev, "rs485-term",
>                                                         GPIOD_OUT_LOW);
> +
> +       if (port->rs485_term_gpio &&

This check is incorrect. Either you need to move that after error
checking (that's what I personally prefer), or use !IS_ERR_OR_NULL().

> +           !(port->rs485_supported->flags & SER_RS485_TERMINATE_BUS)) {
> +               dev_warn(port->dev,
> +                       "%s (%d): RS485 termination gpio not supported by driver\n",
> +                       port->name, port->line);
> +               devm_gpiod_put(dev, port->rs485_term_gpio);
> +               port->rs485_term_gpio = NULL;
> +       }
> +
>         if (IS_ERR(port->rs485_term_gpio)) {
>                 ret = PTR_ERR(port->rs485_term_gpio);
>                 port->rs485_term_gpio = NULL;
Lino Sanfilippo July 4, 2022, 9:01 a.m. UTC | #2
Hi,

On 03.07.22 20:27, Andy Shevchenko wrote:
> On Sun, Jul 3, 2022 at 7:02 PM Lino Sanfilippo <LinoSanfilippo@gmx.de> wrote:
>>
>> From: Lino Sanfilippo <l.sanfilippo@kunbus.com>
>>
>> In uart_get_rs485_mode() only try to get a termination GPIO if RS485 bus
>> termination is supported by the driver. This prevents from allocating
>> and holding a GPIO descriptor for the drivers lifetimg that will never be
>
> lifetiming
>
>> used.
>
> ...
>
>>         port->rs485_term_gpio = devm_gpiod_get_optional(dev, "rs485-term",
>>                                                         GPIOD_OUT_LOW);
>> +
>> +       if (port->rs485_term_gpio &&
>
> This check is incorrect. Either you need to move that after error
> checking (that's what I personally prefer), or use !IS_ERR_OR_NULL().
>

Right, a stupid mistake. I will fix this, thanks!

Regards,
Lino
Lino Sanfilippo July 4, 2022, 3:07 p.m. UTC | #3
On 04.07.22 11:55, Ilpo Järvinen wrote:
> On Sun, 3 Jul 2022, Lino Sanfilippo wrote:
>
>> From: Lino Sanfilippo <l.sanfilippo@kunbus.com>
>>
>> In uart_get_rs485_mode() only try to get a termination GPIO if RS485 bus
>> termination is supported by the driver. This prevents from allocating
>> and holding a GPIO descriptor for the drivers lifetimg that will never be
>> used.
>>
>> Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
>> ---
>>
>> NOTE:
>> This patch follows the design decision that "rs485_supported" is
>> set by the driver at initialization and cannot be modified
>> afterwards. However the better approach would be to let the serial
>> core modify the termination GPIO support setting based on the
>> existence of a termination GPIO. If "rs485_supported" is not a
>> read-only value any more in future the logic implemented in this
>> patch should be adjusted accordingly.
>>
>>  drivers/tty/serial/serial_core.c | 10 ++++++++++
>>  1 file changed, 10 insertions(+)
>>
>> diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
>> index 85ef7ef00b82..3768663dfa4d 100644
>> --- a/drivers/tty/serial/serial_core.c
>> +++ b/drivers/tty/serial/serial_core.c
>> @@ -3404,6 +3404,16 @@ int uart_get_rs485_mode(struct uart_port *port)
>>  	 */
>>  	port->rs485_term_gpio = devm_gpiod_get_optional(dev, "rs485-term",
>>  							GPIOD_OUT_LOW);
>> +
>> +	if (port->rs485_term_gpio &&
>> +	    !(port->rs485_supported->flags & SER_RS485_TERMINATE_BUS)) {
>> +		dev_warn(port->dev,
>> +			"%s (%d): RS485 termination gpio not supported by driver\n",
>> +			port->name, port->line);
>> +		devm_gpiod_put(dev, port->rs485_term_gpio);
>> +		port->rs485_term_gpio = NULL;
>> +	}
>> +
>>  	if (IS_ERR(port->rs485_term_gpio)) {
>>  		ret = PTR_ERR(port->rs485_term_gpio);
>>  		port->rs485_term_gpio = NULL;
>
> I sent a series to embed supported_rs485 to uart_port and manage
> SER_RS485_TERMINATE_BUS properly so I think this won't be necessary
> with that?
>
>

This is why I wrote the "NOTE" above. But yes, this patch is not needed
any more. I will drop it in the next version.


Regards,
Lino
diff mbox series

Patch

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 85ef7ef00b82..3768663dfa4d 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -3404,6 +3404,16 @@  int uart_get_rs485_mode(struct uart_port *port)
 	 */
 	port->rs485_term_gpio = devm_gpiod_get_optional(dev, "rs485-term",
 							GPIOD_OUT_LOW);
+
+	if (port->rs485_term_gpio &&
+	    !(port->rs485_supported->flags & SER_RS485_TERMINATE_BUS)) {
+		dev_warn(port->dev,
+			"%s (%d): RS485 termination gpio not supported by driver\n",
+			port->name, port->line);
+		devm_gpiod_put(dev, port->rs485_term_gpio);
+		port->rs485_term_gpio = NULL;
+	}
+
 	if (IS_ERR(port->rs485_term_gpio)) {
 		ret = PTR_ERR(port->rs485_term_gpio);
 		port->rs485_term_gpio = NULL;