linux-kernel - Re: [PATCH v2 1/1] platform/chrome: Probe multiple i2c adapters of the same name

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Date:	Wed, 11 Jun 2014 12:24:04 +0300
From:	Mika Westerberg <mika.westerberg@...ux.intel.com>
To:	Scot Doyle <lkml14@...tdoyle.com>
Cc:	Benson Leung <bleung@...omium.org>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Olof Johansson <olof@...om.net>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/1] platform/chrome: Probe multiple i2c adapters of
 the same name

On Tue, Jun 10, 2014 at 06:17:35AM +0100, Scot Doyle wrote:
> The chromeos_laptop module probes the first i2c adapter with a specific name
> for expected hardware. However, the Acer C720 Chromebook has two i2c
> adapters with the same name. This patch probes each i2c adapter with a
> specific name in turn, until locating the expected hardware.
> 
> Thanks to Mika Westerberg for identifying the need for unique bus addresses
> within each set of identically-named adapters.
> 
> Signed-off-by: Scot Doyle <lkml14@...tdoyle.com>
> CC: Benson Leung <bleung@...omium.org>
> CC: Mika Westerberg <mika.westerberg@...ux.intel.com>

Few comments about style:

> ---
> diff --git a/drivers/platform/chrome/chromeos_laptop.c
> b/drivers/platform/chrome/chromeos_laptop.c
> index 7f3aad0..8382315 100644
> --- a/drivers/platform/chrome/chromeos_laptop.c
> +++ b/drivers/platform/chrome/chromeos_laptop.c
> @@ -29,6 +29,8 @@
>  #include <linux/module.h>
>  #include <linux/platform_device.h>
> 
> +/* Note: Bus addresses must be unique within each set of identically-named
> +	 adapters on a board, otherwise device probing may fail. */

Check Documentation/CodingStyle about format of block comments.

>  #define ATMEL_TP_I2C_ADDR	0x4b
>  #define ATMEL_TP_I2C_BL_ADDR	0x25
>  #define ATMEL_TS_I2C_ADDR	0x4a
> @@ -173,7 +175,7 @@ static struct i2c_client *__add_probed_i2c_device(
>  	/* add the i2c device */
>  	client = i2c_new_probed_device(adapter, info, addrs, NULL);
>  	if (!client)
> -		pr_err("%s failed to register device %d-%02x\n",
> +		pr_debug("%s did not add i2c device %d-%02x\n",
>  		       __func__, bus, info->addr);
>  	else
>  		pr_debug("%s added i2c device %d-%02x\n",
> @@ -194,13 +196,14 @@ static int __find_i2c_adap(struct device *dev, void *data)
>  	return (strncmp(adapter->name, name, strlen(name)) == 0);
>  }
> 
> -static int find_i2c_adapter_num(enum i2c_adapter_type type)
> +static int find_i2c_next_adapter_num(enum i2c_adapter_type type,
> +				     struct device *start)
>  {
>  	struct device *dev = NULL;
>  	struct i2c_adapter *adapter;
>  	const char *name = i2c_adapter_names[type];
> -	/* find the adapter by name */
> -	dev = bus_find_device(&i2c_bus_type, NULL, (void *)name,
> +	/* find the next adapter by name */
> +	dev = bus_find_device(&i2c_bus_type, start, (void *)name,
>  			      __find_i2c_adap);
>  	if (!dev) {
>  		/* Adapters may appear later. Deferred probing will retry */
> @@ -226,10 +229,17 @@ static struct i2c_client *add_probed_i2c_device(
>  		struct i2c_board_info *info,
>  		const unsigned short *addrs)
>  {
> -	return __add_probed_i2c_device(name,
> -				       find_i2c_adapter_num(type),
> -				       info,
> -				       addrs);
> +	struct i2c_client *client = NULL;
> +	struct device *start = NULL;
> +	int adapter_num = 0;

Please add blank line here.

> +	while (!client && adapter_num > -1) {
> +		adapter_num = find_i2c_next_adapter_num(type, start);
> +		client = __add_probed_i2c_device(name,
> +						 adapter_num,
> +						 info,
> +						 addrs);

Don't the above fit into one line, specifically if you call adapter_num
just num or something like that.

> +	}
> +	return client;
>  }
> 
>  /*
> @@ -242,10 +252,10 @@ static struct i2c_client *add_i2c_device(const char *name,
>  						struct i2c_board_info *info)
>  {
>  	const unsigned short addr_list[] = { info->addr, I2C_CLIENT_END };
> -	return __add_probed_i2c_device(name,
> -				       find_i2c_adapter_num(type),
> -				       info,
> -				       addr_list);
> +	return add_probed_i2c_device(name,
> +				     type,
> +				     info,
> +				     addr_list);

Same here.

>  }
> 
>  static int setup_cyapa_tp(enum i2c_adapter_type type)
--
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