linux-kernel - Re: [PATCH 4/6] tegra, serial8250: add ->handle_break() uart

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Message-ID: <4F7F66A4.8070701@wwwdotorg.org>
Date:	Fri, 06 Apr 2012 15:56:52 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	"Williams, Dan J" <dan.j.williams@...el.com>
CC:	gregkh@...uxfoundation.org,
	Sudhakar Mamillapalli <sudhakar@...com>,
	linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
	Colin Cross <ccross@...roid.com>,
	Olof Johansson <olof@...om.net>,
	Nhan H Mai <nhan.h.mai@...el.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>, alan@...ux.intel.com
Subject: Re: [PATCH 4/6] tegra, serial8250: add ->handle_break() uart_port
 op

On 04/06/2012 03:28 PM, Williams, Dan J wrote:
> On Fri, Apr 6, 2012 at 2:01 PM, Stephen Warren <swarren@...dotorg.org> wrote:
>> On 04/06/2012 12:49 PM, Dan Williams wrote:
>>> The "KT" serial port has another use case for a "received break" quirk,
>>> so before adding another special case to the 8250 core take this
>>> opportunity to push such quirks out of the core and into a uart_port op.
>>
>> This doesn't seem quite right. Why do the board files have to set up
>> this .handle_break function; they're already setting .type=PORT_TEGRA,
>> which should be enough to drive the setup of any required quirks.
> 
> Because struct serial8250_config does not convey any uart_port ops.

But couldn't it be enhanced to do so, just like this patch added a field
to struct uart_port for this? If you went this route, then the change
would be entirely isolated within 8250.c, so you could drop all the
arch/arm/mach-tegra changes, and also not need to update of_serial.c.

>> I'm not sure what the implication is of moving the call to clr_fifo()
>> into uart_handle_break(). What's the benefit of one location over the other?
> 
> This was the location where the core was already doing it's break
> handling, so it made sense to check here if the device had any quirks
> to run.  There shouldn't be any implications because the core was
> already doing clear_rx_fifo() immediately before calling
> uart_handle_break.  Here is the relevant hunk with a bit more context:

Ah OK, that part seems fine then.
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