2.6 I2C re-add i2c_get_client()

PATCH In review [email protected] 2 participants 4 messages Apr 29, 2004 – May 8, 2004 I2C

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[email protected]

author

2004-04-29 14:07 UTC #0 lore raw

PATCH 1/1 2.6 I2C re-add i2c_get_client()

Hi,
here's a patch which re-adds i2c_get_client() back to i2c_core.c. That call was removed in 2003 because there were no users of that function at that time.

I think this call is needed for I2C chip drivers which provide functionality to be used by other driver modules, for example RTC chips or EEPROMs. These chip drivers tend to encapsulate raw i2c chip access and provide function calls for other modulesi, for example via the i2c_driver->command() method.

I tried to get the locking right, so please comment. The patch is against 2.6.6-rc3 and works quite fine with my i2c rtc chip.

Thanks,
Stefan E.

Signature · 3 lines

Eletztrick Computing - Customized Linux Development
Stefan Eletzhofer, Marktstrasse 43, DE-88214 Ravensburg
http://www.eletztrick.de

Add back missing i2c_get_client() call.

#
# Patch managed by http://www.mn-logistik.de/unsupported/pxa250/patcher
#

drivers/i2c/i2c-core.c renamed from drivers/i2c/i2c-core.c~i2c-get-client +52 -0

@@ -412,6 +412,57 @@
 	return res;
 }
 
+struct i2c_client *i2c_get_client(int driver_id, int adapter_id, 
+					struct i2c_client *prev)
+{
+	struct list_head *adap_list;
+	struct list_head *item, *_n;
+	struct i2c_adapter *adap;
+	struct i2c_client *client;
+	int found;
+
+	down(&core_lists);
+
+	adap_list = &adapters;
+	if ( prev ) {
+		/* we start searching at the previous clients adapter */
+		adap_list = &prev->adapter->list;
+	}
+
+	found = 0;
+	client = NULL;
+	list_for_each_entry(adap, adap_list, list) {
+		dev_dbg(&adap->dev, "examining adapter id=%08x\n", adap->id);
+		
+		if ( adapter_id && adap->id != adapter_id )
+			continue; /* not the adapter id we want */
+		
+		list_for_each_safe(item, _n, &adap->clients) {
+			client = list_entry(item, struct i2c_client, list);
+			dev_dbg(&client->dev, "examining client\n");
+			dev_dbg(&client->dev, "driver id=%08x\n", client->driver->id);
+
+			if ( prev && prev == client ) {
+				prev = NULL;
+				continue;
+			}
+			
+			if (client->driver->id != driver_id)
+				continue; /* not the driver id we want */
+
+			if ( client->flags & I2C_CLIENT_ALLOW_USE ) {
+				dev_dbg(&client->dev, "found client\n");
+				found = 1;
+				goto out_unlock;
+			}
+		}
+	}
+
+out_unlock:
+	up(&core_lists);
+	return found?client:NULL;
+}
+
 static int i2c_inc_use_client(struct i2c_client *client)
 {

@@ -1261,6 +1312,7 @@
 EXPORT_SYMBOL(i2c_del_driver);
 EXPORT_SYMBOL(i2c_attach_client);
 EXPORT_SYMBOL(i2c_detach_client);
+EXPORT_SYMBOL(i2c_get_client);
 EXPORT_SYMBOL(i2c_use_client);
 EXPORT_SYMBOL(i2c_release_client);
 EXPORT_SYMBOL(i2c_clients_command);

Greg KH

2004-05-02 06:22 UTC #1 lore raw

Quoted 5 lines · On Thu, Apr 29, 2004 at 04:06:57PM +0200, [email protected] wrote:

Hi,
here's a patch which re-adds i2c_get_client() back to i2c_core.c. That call was removed in 2003 because there were no users of that function at that time.

Quoted 7 lines

I think this call is needed for I2C chip drivers which provide functionality to be used by other driver modules, for example RTC chips or EEPROMs. These chip drivers tend to encapsulate raw i2c chip access and provide function calls for other modulesi, for example via the i2c_driver->command() method.
I tried to get the locking right, so please comment. The patch is against 2.6.6-rc3 and works quite fine with my i2c rtc chip.

Locking looks correct, but you also need to increment either the device's reference count, and/or the module reference count for the client.

Care to fix that up?

thanks,

greg k-h

[email protected]

author

2004-05-02 15:08 UTC #2 lore raw

Quoted 11 lines · Greg KH

Quoted 10 lines · On Thu, Apr 29, 2004 at 04:06:57PM +0200, [email protected] wrote:
Hi,
here's a patch which re-adds i2c_get_client() back to i2c_core.c. That call was removed in 2003 because there were no users of that function at that time.
I think this call is needed for I2C chip drivers which provide functionality to be used by other driver modules, for example RTC chips or EEPROMs. These chip drivers tend to encapsulate raw i2c chip access and provide function calls for other modulesi, for example via the i2c_driver->command() method.

Quoted 6 lines

Quoted 2 lines
I tried to get the locking right, so please comment. The patch is against 2.6.6-rc3 and works quite fine with my i2c rtc chip.
Locking looks correct, but you also need to increment either the device's reference count, and/or the module reference count for the client.

I thought that would be the purpose of i2c_use_client(), like the comment in linux/i2c.h suggests? That call also takes care of the ALLOW_USE flag.

i2c_use_client() increments both the drivers and the adapters module ref count, if I see it correctly. Then it also increments the clients usage count, after checking the ALLOW_MULTIPLE_USE flag.

Its counterpart is i2c_release_client().

Quoted 11 lines

Care to fix that up?
thanks,
greg k-h
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Signature · 3 lines

Eletztrick Computing - Customized Linux Development
Stefan Eletzhofer, Marktstrasse 43, DE-88214 Ravensburg
http://www.eletztrick.de

Greg KH

2004-05-08 00:21 UTC #3 lore raw

Quoted 15 lines · On Sun, May 02, 2004 at 05:08:15PM +0200, [email protected] wrote:

Quoted 14 lines · Greg KH
Quoted 12 lines · On Thu, Apr 29, 2004 at 04:06:57PM +0200, [email protected] wrote:
Hi,
here's a patch which re-adds i2c_get_client() back to i2c_core.c. That call was removed in 2003 because there were no users of that function at that time.
I think this call is needed for I2C chip drivers which provide functionality to be used by other driver modules, for example RTC chips or EEPROMs. These chip drivers tend to encapsulate raw i2c chip access and provide function calls for other modulesi, for example via the i2c_driver->command() method.
I tried to get the locking right, so please comment. The patch is against 2.6.6-rc3 and works quite fine with my i2c rtc chip.

Quoted 6 lines

Quoted 3 lines
Locking looks correct, but you also need to increment either the device's reference count, and/or the module reference count for the client.
I thought that would be the purpose of i2c_use_client(), like the comment in linux/i2c.h suggests? That call also takes care of the ALLOW_USE flag.

Yes, but your new function doesn't call it, right? What happens if the driver goes away between the get_client call and the use_client call? oops...

thanks,

greg k-h