Hello! > Some times ago, Ralf Roesch reported that the memory allocation scheme > used in the i2c eeprom driver was causing trouble on MIPS architecture: > > http://archives.andrew.net.au/lm-sensors/msg07233.html > > The cause of the problems is that we do allocate two structures with a > single kmalloc, which breaks alignment. This doesn't seem to be a > problem on x86, but is on mips and probably on other architectures as > well. It happens that all other chip drivers work the same way too, so > they all would need to be fixed. Instead of splitting one kmalloc in two, it would also be possible to add a "struct i2c_client client" field to each of the *_data structures - the compiler should align all fields appropriately. Probably this way will result in less changes to the code (and also less labels and less error paths). Example patch for lm75 (untested): --- linux/drivers/i2c/chips/lm75.c.sensors-kmalloc 2004-02-18 06:57:11 +0300 +++ linux/drivers/i2c/chips/lm75.c 2004-04-04 00:11:41 +0400 @@ -50,6 +50,7 @@ /* Each client has this additional data */ struct lm75_data { + struct i2c_client client; struct semaphore update_lock; char valid; /* !=0 if following fields are valid */ unsigned long last_updated; /* In jiffies */ @@ -141,16 +142,13 @@ /* OK. For now, we presume we have a valid client. We now create the client structure, even though we cannot fill it completely yet. But it allows us to access lm75_{read,write}_value. */ - if (!(new_client = kmalloc(sizeof(struct i2c_client) + - sizeof(struct lm75_data), - GFP_KERNEL))) { + if (!(data = kmalloc(sizeof(struct lm75_data), GFP_KERNEL))) { err = -ENOMEM; goto exit; } - memset(new_client, 0x00, sizeof(struct i2c_client) + - sizeof(struct lm75_data)); + memset(data, 0x00, sizeof(struct lm75_data)); - data = (struct lm75_data *) (new_client + 1); + new_client = &data->client; i2c_set_clientdata(new_client, data); new_client->addr = address; new_client->adapter = adapter; @@ -204,7 +202,7 @@ return 0; exit_free: - kfree(new_client); + kfree(data); exit: return err; } @@ -212,7 +210,7 @@ static int lm75_detach_client(struct i2c_client *client) { i2c_detach_client(client); - kfree(client); + kfree(i2c_get_clientdata(client)); return 0; } -- Sergey Vlasov -------------- next part -------------- A non-text attachment was scrubbed... Name: not available Type: application/pgp-signature Size: 189 bytes Desc: not available Url : http://lists.lm-sensors.org/pipermail/lm-sensors/attachments/20040404/e3cd9e60/attachment.bin
