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

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Message-ID: <alpine.DEB.2.02.1406100610220.8274@scotdoyle.com>
Date:	Tue, 10 Jun 2014 06:17:35 +0100 (BST)
From:	Scot Doyle <lkml14@...tdoyle.com>
To:	Benson Leung <bleung@...omium.org>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>
cc:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Olof Johansson <olof@...om.net>, linux-kernel@...r.kernel.org
Subject: [PATCH v2 1/1] platform/chrome: Probe multiple i2c adapters of the
 same name

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

  static int setup_cyapa_tp(enum i2c_adapter_type type)
--
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