linux-kernel - Re: [PATCH 1/2] serial: samsung: Move uart_register

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Message-ID: <20140120211601.GB634@kroah.com>
Date:	Mon, 20 Jan 2014 13:16:01 -0800
From:	Greg KH <gregkh@...uxfoundation.org>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	Tushar Behera <tushar.behera@...aro.org>,
	linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
	linux-samsung-soc@...r.kernel.org, jslaby@...e.cz,
	ben.dooks@...ethink.co.uk, broonie@...nel.org
Subject: Re: [PATCH 1/2] serial: samsung: Move uart_register_driver call to
 device probe

On Mon, Jan 20, 2014 at 10:05:30AM +0000, Russell King - ARM Linux wrote:
> On Mon, Jan 20, 2014 at 02:32:34PM +0530, Tushar Behera wrote:
> > uart_register_driver call binds the driver to a specific device
> > node through tty_register_driver call. This should typically happen
> > during device probe call.
> > 
> > In a multiplatform scenario, it is possible that multiple serial
> > drivers are part of the kernel. Currently the driver registration fails
> > if multiple serial drivers with same default major/minor numbers are
> > included in the kernel.
> > 
> > A typical case is observed with amba-pl011 and samsung-uart drivers.
> 
> The samsung-uart driver is at fault here - the major/minor numbers were
> officially registered to amba-pl011.  Samsung needs to be fixed properly.

I agree, the Samsung driver is "broken" here, but that's no reason why
these two drivers can't register with the tty layer _after_ the hardware
is detected, and not before.

That saves resources on systems that build the drivers in, yet do not
have the hardware present, which is always a good thing.

thanks,

greg k-h
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