Re: [PATCH v5 5/7] serial: core, imx: do not set RS485 enabled if it is not supported

["Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>]

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On Sat, 9 Dec 2023, Lino Sanfilippo wrote:

> If the imx driver cannot support RS485 it sets the ports rs485_supported
> structure to NULL.

No, an embedded struct inside struct uart_port cannot be set to NULL, 
it's always there.

Looking into the code, that setting of rs485_supported from imx_no_rs485 
is actually superfluous as it should be already cleared to zeros on alloc.

> But it still calls uart_get_rs485_mode() which may set
> the RS485_ENABLED flag nevertheless.
> 
> This may lead to an attempt to configure RS485 even if it is not supported
> when the flag is evaluated in uart_configure_port() at port startup.
> 
> Avoid this by bailing out of uart_get_rs485_mode() if the RS485_ENABLED
> flag is not supported by the caller.
> 
> With this fix a check for RTS availability is now obsolete in the imx
> driver, since it can not evaluate to true any more. Remove this check, too.
> 
> Fixes: 00d7a00e2a6f ("serial: imx: Fill in rs485_supported")
> Cc: Shawn Guo <shawnguo@kernel.org>
> Cc: Sascha Hauer <s.hauer@pengutronix.de>
> Cc: stable@vger.kernel.org
> Suggested-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>

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 i.