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

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Message-ID: <edbb9e1d-bed4-0850-08f4-029c4fcbfd5c@gmx.de>
Date:   Mon, 14 Feb 2022 16:09:53 +0100
From:   Lino Sanfilippo <LinoSanfilippo@....de>
To:     Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
Cc:     gregkh@...uxfoundation.org, jirislaby@...nel.org,
        linux-arm-kernel@...ts.infradead.org,
        alexandre.belloni@...tlin.com, mcoquelin.stm32@...il.com,
        richard.genoud@...il.com, festevam@...il.com,
        s.hauer@...gutronix.de, linux@...linux.org.uk,
        nicolas.ferre@...rochip.com, alexandre.torgue@...s.st.com,
        ludovic.desroches@...rochip.com, lukas@...ner.de,
        linux-imx@....com, kernel@...gutronix.de,
        linux-serial@...r.kernel.org, shawnguo@...nel.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/9] serial: core: move RS485 configuration tasks from
 drivers into core

Hi,

On 14.02.22 at 08:06, Uwe Kleine-König wrote:
> On Sun, Feb 13, 2022 at 11:27:29PM +0100, Lino Sanfilippo wrote:
>> Several drivers that support setting the RS485 configuration via userspace
>> implement on or more of the following tasks:
>
> s/on/one/

Ok

>
>>
>> - 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 beheviour among all drivers.
>
> s/beheviour/behaviour/
>

Ok

>> Signed-off-by: Lino Sanfilippo <LinoSanfilippo@....de>
>> ---
>>  drivers/tty/serial/serial_core.c | 13 +++++++++++++
>>  1 file changed, 13 insertions(+)
>>
>> diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
>> index 846192a7b4bf..3fab4070359c 100644
>> --- a/drivers/tty/serial/serial_core.c
>> +++ b/drivers/tty/serial/serial_core.c
>> @@ -1282,8 +1282,21 @@ 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)) {
>> +		rs485.flags |= SER_RS485_RTS_ON_SEND;
>> +		rs485.flags &= ~SER_RS485_RTS_AFTER_SEND;
>> +	}
>> +	/* clamp the delays to [0, 100ms] */
>> +	rs485.delay_rts_before_send = min(rs485.delay_rts_before_send, 100U);
>> +	rs485.delay_rts_after_send = min(rs485.delay_rts_after_send, 100U);
>> +	memset(rs485.padding, 0, sizeof(rs485.padding));
>> +
>>  	spin_lock_irqsave(&port->lock, flags);
>>  	ret = port->rs485_config(port, &rs485);
>> +	if (!ret)
>> +		port->rs485 = rs485;
>
> I was only Cc:d for the imx patch (patch #7) and tried to verify the
> claim there that "the serial core already assigns the passed
> configuration to the uart port". That failed when I looked at my kernel
> tree.
>
> So it would be great, if you sent dependencies (or at least a cover
> letter) to all recipients of a given patch to ease review. Also I want
> to suggest to mention uart_set_rs485_config() in the commit log of the
> imx patch (and probably the others) to simplify verifying the claim
> there.
>

Thanks for the review, I will correct the typos in the next version.
I will also cc you directly for the next version if you dont mind.
get_maintainers only spit out "Pengutronix Kernel Team" so I used that
address for the whole series (including the cover letter).


Regards,
Lino