Re: [PATCH 1/8] serial: core: only get RS485 termination gpio if supported

On 23.06.22 at 11:45, Andy Shevchenko wrote:

On Thu, Jun 23, 2022 at 4:00 AM Lino Sanfilippo [off-list ref] wrote:

quoted

On 22.06.22 at 19:04, Andy Shevchenko wrote:

quoted

On Wed, Jun 22, 2022 at 05:46:52PM +0200, Lino Sanfilippo wrote:

quoted

From: Lino Sanfilippo <redacted>

In uart_get_rs485_mode() only try to get a termination GPIO if RS485 bus
termination is supported by the driver.

I'm not sure I got the usefulness of this change.
We request GPIO line as optional, so if one is defined it in the DT/ACPI, then
they probably want to (opportunistically) have it>

With your change it's possible to have a DTS where GPIO line defined in a
broken way and user won't ever know about it, if they are using platforms
without termination support.

This behavior is not introduced with this patch, also in the current code the driver
wont inform the user if it does not make use erroneous defined termination GPIO.

It does. If a previously stale GPIO resource may have deferred a probe
and hence one may debug why the driver is not working, after this
change one may put a stale GPIO resource into DT/ACPI and have nothing
in the result. Meaning the change relaxes validation which I consider
is not good.

Ok I see the point. So what about changing it to:

	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;
	}

This would also be consistent to the warnings we print in uart_sanitize_serial_rs485() for invalid
RS485 settings.


Regards,
Lino




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