linux-kernel - Re: [PATCH v3] serial: 8250: add gpio support to exar

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Message-ID: <20151222103728.GA30453@sudip-pc>
Date:	Tue, 22 Dec 2015 16:07:28 +0530
From:	Sudip Mukherjee <sudipm.mukherjee@...il.com>
To:	Andy Shevchenko <andy.shevchenko@...il.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	Jiri Slaby <jslaby@...e.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>
Subject: Re: [PATCH v3] serial: 8250: add gpio support to exar

On Tue, Dec 22, 2015 at 12:15:18PM +0200, Andy Shevchenko wrote:
> On Tue, Dec 22, 2015 at 12:08 PM, Sudip Mukherjee
> <sudipm.mukherjee@...il.com> wrote:
> > On Tue, Dec 22, 2015 at 11:58:17AM +0200, Andy Shevchenko wrote:
> 
> >> > The only downside is
> >> > that the module gets loaded even if the device is not there.
> >>
> >> How is that?
> >
> > Alan explained that in https://lkml.org/lkml/2015/12/20/103
> >
> > Quoting from his mail "you reference the methods in it so it will
> > always be dragged in".
> >
> > And I wanted to verify that so I tested today morning after removing the
> > card from my local system and after booting I saw having 8250_gpi loaded.
> 
> Ah, it is in case "exar as a library".
> 
> In case "exar as a separate driver" other way around: it will drag
> methods from 8250_pci if any.

Yes. Now we have many different options:

1) the way i submited v1, 8250_gpio is a separate module, init() and
exit() are referenced from 8250_pci(). Downside - module will be loaded
even if hardware is not there.

2) Separate 8250_exar driver which uses 8250_pci as library. Reason to
avoid - Greg was initially against this idea of having it as a separate
driver.

3) Like Alan suggested, having something like a platform driver and
8250_gpio will bind to that.

I am waiting for Greg's signal on these three and I wont be surprised if
he comes out with another fourth idea which will solve it in a most simple
way. :)

regards
sudip
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