Re: [PATCH 2/2 v5] tty/serial/8250: use mctrl_gpio helpers

[Stefan Roese]

On 11.06.19 14:44, Andy Shevchenko wrote:
> On Tue, Jun 11, 2019 at 12:56:03PM +0200, Stefan Roese wrote:
> > From: Yegor Yefremov <yegorslists@xxxxxxxxxxxxxx>
> >
> > This patch permits the usage for GPIOs to control
> > the CTS/RTS/DTR/DSR/DCD/RI signals.
>
> >   static inline void serial8250_out_MCR(struct uart_8250_port *up, int value)
> >   {
> >   	serial_out(up, UART_MCR, value);
> > +
> > +	if (up->gpios) {
> > +		int mctrl_gpio = 0;
> > +
> > +		if (value & UART_MCR_RTS)
> > +			mctrl_gpio |= TIOCM_RTS;
> > +		if (value & UART_MCR_DTR)
> > +			mctrl_gpio |= TIOCM_DTR;
> > +
> > +		mctrl_gpio_set(up->gpios, mctrl_gpio);
> > +	}
> >   }
> >   
> >   static inline int serial8250_in_MCR(struct uart_8250_port *up)
> >   {
> > -	return serial_in(up, UART_MCR);
> > +	int mctrl;
> > +
> > +	mctrl = serial_in(up, UART_MCR);
> > +
> > +	if (up->gpios) {
> > +		int mctrl_gpio = 0;
> > +
> > +		/* save current MCR values */
> > +		if (mctrl & UART_MCR_RTS)
> > +			mctrl_gpio |= TIOCM_RTS;
> > +		if (mctrl & UART_MCR_DTR)
> > +			mctrl_gpio |= TIOCM_DTR;
> > +
> > +		mctrl_gpio = mctrl_gpio_get_outputs(up->gpios, &mctrl_gpio);
> > +		if (mctrl_gpio & TIOCM_RTS)
> > +			mctrl |= UART_MCR_RTS;
> > +		else
> > +			mctrl &= ~UART_MCR_RTS;
> > +
> > +		if (mctrl_gpio & TIOCM_DTR)
> > +			mctrl |= UART_MCR_DTR;
> > +		else
> > +			mctrl &= ~UART_MCR_DTR;
> > +	}
> > +
> > +	return mctrl;
> >   }
>
> These are using OR logic with potentially volatile data. Shouldn't we mask
> unused bits in UART_MCR in case of up->gpios != NULL?

Sorry, I don't see, which bits you are referring to? Could you please be
a bit more specific with the variable / macro meant (example)?
 
> > +	if (up->gpios == 0)
>
> This is type inconsistency with this check as far as I understand.
> I guess you have to do either (up->gpios == NULL), or (!up->gpios).

Ah, right. Thanks for spotting.

Thanks,
Stefan