Re: [PATCH v3 1/9] serial: core: move RS485 configuration tasks from drivers into core

From: Jiri Slaby <jirislaby@kernel.org>
To: Lino Sanfilippo <LinoSanfilippo@gmx.de>,
	gregkh@linuxfoundation.org, u.kleine-koenig@pengutronix.de
Cc: linux-arm-kernel@lists.infradead.org,
	alexandre.belloni@bootlin.com, mcoquelin.stm32@gmail.com,
	richard.genoud@gmail.com, festevam@gmail.com,
	s.hauer@pengutronix.de, linux@armlinux.org.uk,
	alexandre.torgue@foss.st.com, ludovic.desroches@microchip.com,
	lukas@wunner.de, linux-imx@nxp.com, kernel@pengutronix.de,
	linux-serial@vger.kernel.org, shawnguo@kernel.org,
	linux-stm32@st-md-mailman.stormreply.com,
	linux-kernel@vger.kernel.org, p.rosenberger@kunbus.com
Subject: Re: [PATCH v3 1/9] serial: core: move RS485 configuration tasks from drivers into core
Date: Tue, 22 Feb 2022 07:52:36 +0100	[thread overview]
Message-ID: <8c65bc42-438e-bf3e-fb76-2a4cbc7296c0@kernel.org> (raw)
In-Reply-To: <e883ccb5-68ea-f802-e4fd-864672d8ad7b@kernel.org>

On 22. 02. 22, 7:51, Jiri Slaby wrote:
> On 22. 02. 22, 2:14, Lino Sanfilippo wrote:
>> Several drivers that support setting the RS485 configuration via 
>> userspace
>> implement one or more of the following tasks:
>>
>> - in case of an invalid RTS configuration (both RTS after send and RTS on
>>    send set or both unset) fall back to enable RTS on send and disable 
>> RTS
>>    after send
>>
>> - nullify the padding field of the returned serial_rs485 struct
>>
>> - copy the configuration into the uart port struct
>>
>> - limit RTS delays to 100 ms
>>
>> Move these tasks into the serial core to make them generic and to provide
>> a consistent behaviour among all drivers.
>>
>> Signed-off-by: Lino Sanfilippo <LinoSanfilippo@gmx.de>
>> ---
>>   drivers/tty/serial/serial_core.c | 29 +++++++++++++++++++++++++++++
>>   1 file changed, 29 insertions(+)
>>
>> diff --git a/drivers/tty/serial/serial_core.c 
>> b/drivers/tty/serial/serial_core.c
>> index 846192a7b4bf..2b3afe038c1c 100644
>> --- a/drivers/tty/serial/serial_core.c
>> +++ b/drivers/tty/serial/serial_core.c
>> @@ -42,6 +42,11 @@ static struct lock_class_key port_lock_key;
>>   #define HIGH_BITS_OFFSET    ((sizeof(long)-sizeof(int))*8)
>> +/*
>> + * Max time with active RTS before/after data is sent.
>> + */
>> +#define RS485_MAX_RTS_DELAY    100 /* msecs */
>> +
>>   static void uart_change_speed(struct tty_struct *tty, struct 
>> uart_state *state,
>>                       struct ktermios *old_termios);
>>   static void uart_wait_until_sent(struct tty_struct *tty, int timeout);
>> @@ -1282,8 +1287,32 @@ static int uart_set_rs485_config(struct 
>> uart_port *port,
>>       if (copy_from_user(&rs485, rs485_user, sizeof(*rs485_user)))
>>           return -EFAULT;
>> +    /* pick sane settings if the user hasn't */
>> +    if (!(rs485.flags & SER_RS485_RTS_ON_SEND) ==
>> +        !(rs485.flags & SER_RS485_RTS_AFTER_SEND)) {
>> +        pr_warn("invalid RTS setting, using RTS_ON_SEND instead\n");
> 
> Can't we have a device prefix here, so that everyone knows what device 
> is affected? Without that, it's not that useful. At least port->name & 
> port->line could be printed. The uart core uses dev_* prints, but prints 
> also line as uport->dev can be NULL sometimes.

And this comes from userspace, so should be ratelimited.

-- 
js
suse labs

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