linux-kernel - Re: [PATCH 2 1/9] serial: core: move RS485 configuration tasks from drivers into core

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Date:   Tue, 22 Feb 2022 00:19:24 +0100
From:   Lino Sanfilippo <LinoSanfilippo@....de>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     jirislaby@...nel.org, u.kleine-koenig@...gutronix.de,
        linux@...linux.org.uk, richard.genoud@...il.com,
        nicolas.ferre@...rochip.com, alexandre.belloni@...tlin.com,
        ludovic.desroches@...rochip.com, shawnguo@...nel.org,
        s.hauer@...gutronix.de, kernel@...gutronix.de, festevam@...il.com,
        linux-imx@....com, mcoquelin.stm32@...il.com,
        alexandre.torgue@...s.st.com, linux-serial@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-stm32@...md-mailman.stormreply.com, lukas@...ner.de
Subject: Re: [PATCH 2 1/9] serial: core: move RS485 configuration tasks from
 drivers into core


Hi,

On 21.02.22 at 19:39, Greg KH wrote:

>> diff --git a/include/uapi/linux/serial.h b/include/uapi/linux/serial.h
>> index fa6b16e5fdd8..859045a53231 100644
>> --- a/include/uapi/linux/serial.h
>> +++ b/include/uapi/linux/serial.h
>> @@ -128,6 +128,9 @@ struct serial_rs485 {
>>  							   (if supported) */
>>  	__u32	delay_rts_before_send;	/* Delay before send (milliseconds) */
>>  	__u32	delay_rts_after_send;	/* Delay after send (milliseconds) */
>> +#define SER_RS485_MAX_RTS_DELAY		100		/* Max time with active
>> +							   RTS before/after
>> +							   data sent (msecs) */
>
> Why is this a userspace value now?  What can userspace do with this
> number?  Once we add this, it's fixed for forever.
>
> thanks,
>
> greg k-h
>


Ok, I think we do not really need to expose it to userspace, since we
clamp the delay anyway if it is too big. I will correct this in the next
patch version.

Regards,
Lino