linux-kernel - Re: [PATCH 22/36] serial: Sanitize rs485

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Message-ID: <20220625201232.GA17597@wunner.de>
Date:   Sat, 25 Jun 2022 22:12:32 +0200
From:   Lukas Wunner <lukas@...ner.de>
To:     Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Cc:     linux-serial@...r.kernel.org, Greg KH <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        linux-kernel@...r.kernel.org,
        Lino Sanfilippo <LinoSanfilippo@....de>
Subject: Re: [PATCH 22/36] serial: Sanitize rs485_struct

On Mon, Jun 06, 2022 at 01:04:19PM +0300, Ilpo Järvinen wrote:
> -	if (rs485->delay_rts_before_send > RS485_MAX_RTS_DELAY) {
> +	if (!port->rs485_supported->delay_rts_before_send) {
> +		if (rs485->delay_rts_before_send) {
> +			dev_warn_ratelimited(port->dev,
> +				"%s (%d): RTS delay before sending not supported\n",
> +				port->name, port->line);
> +		}
> +		rs485->delay_rts_before_send = 0;
> +	} else if (rs485->delay_rts_before_send > RS485_MAX_RTS_DELAY) {
>  		rs485->delay_rts_before_send = RS485_MAX_RTS_DELAY;
>  		dev_warn_ratelimited(port->dev,
>  			"%s (%d): RTS delay before sending clamped to %u ms\n",
>  			port->name, port->line, rs485->delay_rts_before_send);
>  	}

This series seems to set rs485_supported->delay_rts_before_send to 1
in all drivers to indicate that a delay is supported.

It would probably be smarter to define it as a maximum, i.e. drivers
declare the supported maximum delay in their rs485_supported struct
and the core can use that to clamp the value.  Initially, all drivers
may use RS485_MAX_RTS_DELAY.  Some chips only support specific delays
(multiples of the UART clock or baud clock).  We can amend their
drivers later according to their capabilities.

Thanks,

Lukas