linux-kernel - Re: [PATCH 1/5] USB : serial : remove tty arg of handle_dcd

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Date:	Tue, 10 Sep 2013 10:09:53 +0200
From:	Paul Chavent <Paul.Chavent@...ra.fr>
To:	Johan Hovold <jhovold@...il.com>
CC:	linux-usb@...r.kernel.org, gregkh@...uxfoundation.org,
	fschaefer.oss@...glemail.com, jslaby@...e.cz, max@...e.de,
	giometti@...eenne.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/5] USB : serial : remove tty arg of handle_dcd_change.



On 09/09/2013 07:45 PM, Johan Hovold wrote:
> On Mon, Sep 09, 2013 at 06:01:16PM +0200, Paul Chavent wrote:
>> Do the same way as in serialcore.c for uart_handle_dcd_change.  It
>> removes duplicated code around the usb_serial_handle_dcd_change calls.
>>
>> Signed-off-by: Paul Chavent <paul.chavent@...ra.fr>
>> ---
>>   drivers/usb/serial/ch341.c   | 7 ++-----
>>   drivers/usb/serial/generic.c | 4 ++--
>>   drivers/usb/serial/pl2303.c  | 7 +------
>>   include/linux/usb/serial.h   | 1 -
>>   4 files changed, 5 insertions(+), 14 deletions(-)
>>
>> diff --git a/drivers/usb/serial/ch341.c b/drivers/usb/serial/ch341.c
>> index c2a4171..51c3d3a 100644
>> --- a/drivers/usb/serial/ch341.c
>> +++ b/drivers/usb/serial/ch341.c
>> @@ -481,11 +481,8 @@ static void ch341_read_int_callback(struct urb *urb)
>>   		spin_unlock_irqrestore(&priv->lock, flags);
>>
>>   		if ((priv->line_status ^ prev_line_status) & CH341_BIT_DCD) {
>> -			struct tty_struct *tty = tty_port_tty_get(&port->port);
>> -			if (tty)
>> -				usb_serial_handle_dcd_change(port, tty,
>> -					    priv->line_status & CH341_BIT_DCD);
>> -			tty_kref_put(tty);
>> +			usb_serial_handle_dcd_change(port,
>> +				    priv->line_status & CH341_BIT_DCD);
>>   		}
>>
>>   		wake_up_interruptible(&port->port.delta_msr_wait);
>> diff --git a/drivers/usb/serial/generic.c b/drivers/usb/serial/generic.c
>> index 1f31e6b..33f1df1 100644
>> --- a/drivers/usb/serial/generic.c
>> +++ b/drivers/usb/serial/generic.c
>> @@ -560,13 +560,13 @@ EXPORT_SYMBOL_GPL(usb_serial_handle_break);
>>   /**
>>    *	usb_serial_handle_dcd_change - handle a change of carrier detect state
>>    *	@port: usb_serial_port structure for the open port
>> - *	@tty: tty_struct structure for the port
>>    *	@status: new carrier detect status, nonzero if active
>>    */
>>   void usb_serial_handle_dcd_change(struct usb_serial_port *usb_port,
>> -				struct tty_struct *tty, unsigned int status)
>> +				unsigned int status)
>>   {
>>   	struct tty_port *port = &usb_port->port;
>> +	struct tty_struct *tty = port->tty;
>
> No, this is not right. There's a reason tty_port_tty_get was used. You
> cannot simply remove it (even if your next patch adds it back, but
> without the NULL check).
>
> I'm actually preparing a series of changes to the MSR handling and
> considered doing something like this, but came to the conclusion that
> keeping the current interface was preferred (e.g. the same reference
> could be used to add handle CTS changes as well). I'm refactoring at a
> different level instead.
>
> I suggest keeping the current interface for a while still, and that you
> add the tty_port_tty_get to your ftdi patch instead.
>
> Johan
>

Hi.

If a refactoring is in progress, the code in driver/tty/serial_core.c 
should be considered too. The signature of handle_dcd_change is simply :

void uart_handle_dcd_change(struct uart_port *uport, unsigned int status);

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