linux-kernel - Re: [PATCH v8 3/3] tty: 8250_omap: Use software emulated RS485 direction control

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Message-ID: <CAEo2pzs7mTUFpUGvsyrzt5cYPXsWLiBLaoQ==SypBm5fKjkFjA@mail.gmail.com>
Date:	Thu, 11 Feb 2016 23:19:52 +0300
From:	Ильяс Гасанов 
	<torso.nafi@...il.com>
To:	"Matwey V. Kornilov" <matwey@....msu.ru>
Cc:	Greg KH <gregkh@...uxfoundation.org>, Jiri Slaby <jslaby@...e.com>,
	Peter Hurley <peter@...leysoftware.com>,
	Andy Shevchenko <andy.shevchenko@...il.com>,
	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-serial@...r.kernel.org
Subject: Re: [PATCH v8 3/3] tty: 8250_omap: Use software emulated RS485
 direction control

2016-02-11 22:08 GMT+03:00 Matwey V. Kornilov <matwey@....msu.ru>:
> Thanks for pointing out. serial8250_unregister_port should set
> serial8250_ports[line].em485 to NULL in order to prevent unneeded
> activation when this struct is reused.

Then the allocated/initialized resources should be freed/released as well.

> You would be able to use serial8250_em485_register in omap8250_probe
> on &up before serial8250_register_8250_port(&up) if
> serial8250_register_8250_port could replicate em485 member state.
> But there are alternatives in implementation.

I'm considering adding the relevant code to the omap8250_startup and
omap8250_shutdown callback functions. However the serial driver
documentation claims that these don't have port->lock taken when
invoked, only port_sem.

> serial8250_register_8250_port may either copy pointer up->em485 to
> uart->em485 or perform deep copy.

Actually, "up" here in omap8250_probe is not a pointer but a struct
variable on stack, so copying the pointer to it is out of question.


Regards,
Ilyas G.