linux-kernel - Re: [PATCH 17/36] usb: serial: ti_usb_3410_5052: Remove useless tty

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Date:	Fri, 15 Jul 2016 13:33:59 +0200
From:	Johan Hovold <johan@...nel.org>
To:	Mathieu OTHACEHE <m.othacehe@...il.com>
Cc:	johan@...nel.org, gregkh@...uxfoundation.org,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 17/36] usb: serial: ti_usb_3410_5052: Remove useless
 tty_wakeup

On Thu, May 12, 2016 at 10:48:49AM +0200, Mathieu OTHACEHE wrote:
> The generic driver doesn't call tty_wakeup in
> usb_serial_generic_msr_changed so this tty_wakeup seems useless.

While we strive to have the generic implementation as complete as
possible, it not doing something does not mean it must not be done. :)

> Signed-off-by: Mathieu OTHACEHE <m.othacehe@...il.com>
> ---
>  drivers/usb/serial/ti_usb_3410_5052.c | 9 ---------
>  1 file changed, 9 deletions(-)
> 
> diff --git a/drivers/usb/serial/ti_usb_3410_5052.c b/drivers/usb/serial/ti_usb_3410_5052.c
> index 5ef721c..3f2372e 100644
> --- a/drivers/usb/serial/ti_usb_3410_5052.c
> +++ b/drivers/usb/serial/ti_usb_3410_5052.c
> @@ -1238,7 +1238,6 @@ static int ti_set_serial_info(struct tty_struct *tty, struct ti_port *tport,
>  static void ti_handle_new_msr(struct ti_port *tport, u8 msr)
>  {
>  	struct async_icount *icount;
> -	struct tty_struct *tty;
>  	unsigned long flags;
>  
>  	dev_dbg(&tport->tp_port->dev, "%s - msr 0x%02X\n", __func__, msr);
> @@ -1259,14 +1258,6 @@ static void ti_handle_new_msr(struct ti_port *tport, u8 msr)
>  	}
>  
>  	tport->tp_msr = msr & TI_MSR_MASK;
> -
> -	/* handle CTS flow control */
> -	tty = tty_port_tty_get(&tport->tp_port->port);
> -	if (tty && C_CRTSCTS(tty)) {
> -		if (msr & TI_MSR_CTS)
> -			tty_wakeup(tty);
> -	}
> -	tty_kref_put(tty);

That said, this particular change does seem correct, as any writers
would have been woken up once any blocked (nacked) bulk-out transfers
complete.

Thanks,
Johan