linux-kernel - Re: [RESEND RFC PATCH 1/5] platform: x86: add driver for UP Board I/O CPLD

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Date:	Fri, 22 Jul 2016 17:11:31 -0400
From:	Paul Gortmaker <paul.gortmaker@...driver.com>
To:	Darren Hart <dvhart@...radead.org>
Cc:	"Dan O'Donovan" <dan@...tex.com>,
	platform-driver-x86@...r.kernel.org,
	Lee Jones <lee.jones@...aro.org>,
	andriy.shevchenko@...ux.intel.com, mika.westerberg@...ux.intel.com,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RESEND RFC PATCH 1/5] platform: x86: add driver for UP Board I/O CPLD

On Fri, Jul 22, 2016 at 4:52 PM, Darren Hart <dvhart@...radead.org> wrote:
> On Mon, Jul 04, 2016 at 05:07:10PM +0100, Dan O'Donovan wrote:
>> The UP board utilises a CPLD between its Intel X5-Z8350 SoC and an
>> external 40-pin header, to provide buffered voltage level-shifting
>> of the I/O signals, mux switching and LED control, and programmable
>> pin mapping between the SoC and the external pin header.
>>
>> gpio, pinctrl and led drivers are provided in separate commits
>> to manage the functions provided by that CPLD.
>>
>> This commit registers a platform driver to manage the configuration
>> of the CPLD itself.
>>
>> Signed-off-by: Dan O'Donovan <dan@...tex.com>
>> ---
>>  drivers/platform/x86/up_board_cpld.c | 560 +++++++++++++++++++++++++++++++++++
>>  drivers/platform/x86/up_board_cpld.h |  38 +++
>>  2 files changed, 598 insertions(+)

A variation on what Darren said but leading to the same issue;
i.e. importance of bisection is the presence of only two files here.

Normally there should be a Makefile change and possibly a
Kconfig change (addition) that bind the driver in so it can be
built.

However, since those are not shown here, I can't tell if the use
of module.h makes sense, because I can't see if the Kconfig
is bool or tristate.   So it goes beyond bisectability and also
impacts ability to properly review -- the "it" here  being the
proper segmentation of a patch series.

Thanks,
Paul.
--

>>  create mode 100644 drivers/platform/x86/up_board_cpld.c
>>  create mode 100644 drivers/platform/x86/up_board_cpld.h
>>
>> diff --git a/drivers/platform/x86/up_board_cpld.c b/drivers/platform/x86/up_board_cpld.c
>> new file mode 100644
>> index 0000000..dc36d6a
>> --- /dev/null
>> +++ b/drivers/platform/x86/up_board_cpld.c
>> @@ -0,0 +1,560 @@
>> +/*
>> + * UP Board I/O Header CPLD driver.
>> + *
>> + * Copyright (c) 2016, Emutex Ltd.  All rights reserved.
>> + *
>> + * Author: Dan O'Donovan <dan@...tex.com>
>> + *
>> + * This program is free software; you can redistribute it and/or modify it
>> + * under the terms and conditions of the GNU General Public License,
>> + * version 2, as published by the Free Software Foundation.
>> + *
>> + * This program is distributed in the hope it will be useful, but WITHOUT
>> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
>> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
>> + * more details.
>> + *
>> + * You should have received a copy of the GNU General Public License
>> + * along with this program.  If not, see <http://www.gnu.org/licenses/>.
>> + */
>> +#include <linux/kernel.h>
>> +#include <linux/module.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/spinlock.h>
>> +#include <linux/gpio.h>
>> +
>> +#include "up_board_cpld.h"
>> +#include "up_board_pinctrl.h"
>
> Here you include up_board_pinctrl.h, but this file has not been introduced. The
> build fails with 1/5 applied, breaking bisection.
>
> Something to keep in mind as you relocate and refactor these drivers as we hear
> back from the other maintainers. Each patch should build as you know, I'm sure
> this was an error following a refactoring or something similar.
>
> --
> Darren Hart
> Intel Open Source Technology Center