linux-kernel - Re: [PATCH 1/2] serial/8250: Add support for RS485 IOCTLs

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Message-ID: <20140731150753.3f12fc2f@alan.etchedpixels.co.uk>
Date:	Thu, 31 Jul 2014 15:07:53 +0100
From:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>
To:	Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.cz>, Alan Cox <alan@...ux.intel.com>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Murali Karicheri <m-karicheri2@...com>,
	Jingoo Han <jg1.han@...sung.com>,
	Michael Welling <mwelling@...e.org>,
	Peter Hurley <peter@...leysoftware.com>,
	Joe Schultz <jschultz@...-inc.com>,
	Ingo Molnar <mingo@...e.hu>,
	Doug Anderson <dianders@...omium.org>,
	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] serial/8250: Add support for RS485 IOCTLs

> This patch allow the users of the 8250 infrastructure to define a
> handler for RS485 configration.

This feels to me like the right code in the wrong place.
 
> If no handler is defined the 8250 driver will work as usual.

Is there any reasons we can't have uart_ops.rs485_config and the RS485
ioctl logic in the serial_core, or even push rs485_get/put into the tty
ioctl handler and tty ops so it's not duplicated everywhere ?
 
> +	switch (cmd) {
> +	case TIOCSRS485:
> +		if (copy_from_user(&rs485_config, (void __user *)arg,
> +				   sizeof(rs485_config)))
> +			return -EFAULT;
> +
> +		ret = up->rs485_config(up, &rs485_config);
> +		if (ret)
> +			return ret;
> +
> +		memcpy(&up->rs485, &rs485_config, sizeof(rs485_config));
> +
> +		return 0;
> +	case TIOCGRS485:
> +		if (copy_to_user((void __user *)arg, &up->rs485,
> +				 sizeof(up->rs485)))
> +			return -EFAULT;
> +		return 0;

Possibly your mutex needs to cover parallel get an set, but then again
anyone doing that may well deserve what they get 8)

Alan
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