linux-kernel - Re: [PATCH v5 2/2] i2c: sunxi: add P2WI (Push/Pull 2 Wire Interface) controller support

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Message-ID: <53980883.5030402@free-electrons.com>
Date:	Wed, 11 Jun 2014 09:42:59 +0200
From:	Boris BREZILLON <boris.brezillon@...e-electrons.com>
To:	Wolfram Sang <wsa@...-dreams.de>
CC:	Randy Dunlap <rdunlap@...radead.org>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Hans de Goede <hdegoede@...hat.com>,
	Shuge <shuge@...winnertech.com>, kevin@...winnertech.com,
	devicetree@...r.kernel.org, linux-doc@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-i2c@...r.kernel.org
Subject: Re: [PATCH v5 2/2] i2c: sunxi: add P2WI (Push/Pull 2 Wire Interface)
 controller support

Hello Wolfram,

On 10/06/2014 21:45, Wolfram Sang wrote:
> Hi,
>
> compiling this driver gives me:
>
> drivers/i2c/busses/i2c-sun6i-p2wi.c: In function 'p2wi_probe':
> drivers/i2c/busses/i2c-sun6i-p2wi.c:272:2: error: implicit declaration of function 'devm_reset_control_get' [-Werror=implicit-function-declaration]
> drivers/i2c/busses/i2c-sun6i-p2wi.c:272:13: warning: assignment makes pointer from integer without a cast [enabled by default]

Yes, there's a missing "depends on RESET_CONTROLLER" in the Kconfig
entry, which I didn't notice because this option was selected by the
sun6i platform.

>> diff --git a/drivers/i2c/busses/i2c-sun6i-p2wi.c b/drivers/i2c/busses/i2c-sun6i-p2wi.c
>> new file mode 100644
>> index 0000000..4f7b93f
>> --- /dev/null
>> +++ b/drivers/i2c/busses/i2c-sun6i-p2wi.c
>> @@ -0,0 +1,356 @@
>> +/*
>> + * P2WI (Push-Pull Two Wire Interface) bus driver.
>> + *
>> + * Author: Boris BREZILLON <boris.brezillon@...e-electrons.com>
>> + *
>> + * This file is licensed under the terms of the GNU General Public License
>> + * version 2.  This program is licensed "as is" without any warranty of any
>> + * kind, whether express or implied.
>> + *
>> + * The P2WI controller looks like an SMBus controller which only supports byte
>> + * data transfers. But, it differs from standard SMBus protocol on several
>> + * aspects:
>> + * - it supports only one slave device, and thus drop the address field
>> + * - it adds a parity bit every 8bits of data
>> + * - only one read access is required to read a byte (instead of a write
>> + *   followed by a read access in standard SMBus protocol)
>> + * - there's no Ack bit after each byte transfer
>> + *
>> + * This means this bus cannot be used to interface with standard SMBus
>> + * devices (the only known device to support this interface is the AXP221
>> + * PMIC).
>> + *
>> + */
>> +#include <linux/kernel.h>
>> +#include <linux/slab.h>
>> +#include <linux/module.h>
>> +#include <linux/spinlock.h>
> Unneeded. Please check other includes, too.

Okay, I'll clean it up.
>
>> +#include <linux/i2c.h>
>> +#include <linux/interrupt.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/io.h>
>> +#include <linux/of.h>
>> +#include <linux/of_device.h>
>> +#include <linux/of_irq.h>
>> +#include <linux/clk.h>
>> +#include <linux/err.h>
>> +#include <linux/delay.h>
>> +#include <linux/clk.h>
>> +#include <linux/reset.h>
>> +
> ...
>
>> +	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>> +	p2wi->regs = devm_ioremap_resource(dev, r);
>> +	if (IS_ERR(p2wi->regs)) {
>> +		ret = PTR_ERR(p2wi->regs);
>> +		return ret;
>> +	}
> return PTR_ERR(...)?

Oops, some vestige of my previous dev_err call.

>
>> +
>> +	snprintf(p2wi->adapter.name, sizeof(p2wi->adapter.name), pdev->name);
>> +	irq = platform_get_irq(pdev, 0);
>> +	if (irq < 0) {
>> +		dev_err(dev, "failed to retrieve irq: %d\n", ret);
>> +		return irq;
>> +	}
>> +
>> +	p2wi->clk = devm_clk_get(dev, NULL);
>> +	if (IS_ERR(p2wi->clk)) {
>> +		ret = PTR_ERR(p2wi->clk);
>> +		dev_err(dev, "failed to retrieve clk: %d\n",
>> +			ret);
> dangling ret.

I'll fix it.

Thanks,

Boris

-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

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