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List:       linux-serial
Subject:    Re: [PATCH 1/6] serial: sa1100: add support for mctrl gpios
From:       Uwe =?iso-8859-1?Q?Kleine-K=F6nig?=  <u.kleine-koenig () pengutronix ! de>
Date:       2019-05-31 15:10:32
Message-ID: 20190531151032.tfrl7yqph6wsg5pl () pengutronix ! de
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On Fri, May 31, 2019 at 03:01:28PM +0100, Russell King - ARM Linux admin wrote:
> On Fri, May 31, 2019 at 03:56:58PM +0200, Uwe Kleine-König wrote:
> > Unless I miss something (which is quite possible given that it's quite
> > some time ago I looked into mctrl_gpio) with mctrl_gpio_init_noauto()
> > having a CTS-gpio is just ignored unless the modem ctrl lines are
> > explicitely requestet while with mctrl_gpio_init() it results in an
> > error. Isn't the error the better alternative?
> 
> Unless the serial driver polls the modem control line status, which
> the SA1100 driver continues to do in exactly the same way after this
> conversion.
> 
> Do you suggest that we just regress the driver by ripping out this
> support that no one has had any problems with, and that is known to
> work sufficiently in its day, just because we now don't like it?

No, of course not. A nice improvement would be to teach gpio_mctrl (or
serial core?) about polling. But this is of course out of scope for this
patch, so I suggest to stay with mctrl_gpio_init_noauto and document the
lack of irq-capability somewhere prominently such that someone who picks
up converting mctrl_gpio_init_noauto to mctrl_gpio_init notices this
problem before actually hitting it.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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