From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262562AbVBXXec (ORCPT ); Thu, 24 Feb 2005 18:34:32 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262571AbVBXXd4 (ORCPT ); Thu, 24 Feb 2005 18:33:56 -0500 Received: from rwcrmhc14.comcast.net ([216.148.227.89]:30685 "EHLO rwcrmhc11.comcast.net") by vger.kernel.org with ESMTP id S262558AbVBXX3i (ORCPT ); Thu, 24 Feb 2005 18:29:38 -0500 Message-ID: <421E6361.90009@acm.org> Date: Thu, 24 Feb 2005 17:29:37 -0600 From: Corey Minyard User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.3) Gecko/20040913 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Greg KH Cc: Andrew Morton , lkml Subject: [PATCH] I2C patch 3 - Add handling for I2C operation queue entries Content-Type: multipart/mixed; boundary="------------030405070502080907060108" Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org This is a multi-part message in MIME format. --------------030405070502080907060108 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit This is one in a series of patches for adding a non-blocking interface to the I2C driver for supporting the IPMI SMBus driver. --------------030405070502080907060108 Content-Type: text/plain; name="i2c_opq_handling.diff" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="i2c_opq_handling.diff" This patch adds handling of the op q to the I2C main code in preparation for the non-blocking changes. Signed-off-by: Corey Minyard Index: linux-2.6.11-rc4/drivers/i2c/i2c-core.c =================================================================== --- linux-2.6.11-rc4.orig/drivers/i2c/i2c-core.c +++ linux-2.6.11-rc4/drivers/i2c/i2c-core.c @@ -54,6 +54,8 @@ complete(&adap->dev_released); } +#define entry_completed(e) (atomic_read(&(e)->completed) <= 0) + static struct device_driver i2c_adapter_driver = { .name = "i2c_adapter", .bus = &i2c_bus_type, @@ -134,6 +136,8 @@ } adap->nr = id & MAX_ID_MASK; + spin_lock_init(&adap->q_lock); + INIT_LIST_HEAD(&adap->q); init_MUTEX(&adap->bus_lock); init_MUTEX(&adap->clist_lock); list_add_tail(&adap->list,&adapters); @@ -1334,6 +1338,100 @@ return (func & adap_func) == func; } +/* ---------------------------------------------------- + * Entry handling + * ---------------------------------------------------- + */ + +/* Get the first entry off the head of the queue and lock it there. + The entry is guaranteed to remain first in the list and the handler + not be called until i2c_entry_put() is called. */ +static struct i2c_op_q_entry *_i2c_entry_get(struct i2c_adapter * adap) +{ + struct i2c_op_q_entry * entry = NULL; + + if (!list_empty(&adap->q)) { + struct list_head * link = adap->q.next; + entry = list_entry(link, struct i2c_op_q_entry, link); + if (entry_completed(entry)) + entry = NULL; + else { + int val = atomic_add_return(1, &entry->usecount); + + /* This is subtle. If we increment the + usecount and the value is 1, that means it + was zero before. This means the put() + routine has decremented the value to zero + and is between tha decrement and the + spinlock. In this case, return NULL + because the current list head is complete + and the next list item is not yet + started. */ + if (val == 1) { + atomic_dec(&entry->usecount); + entry = NULL; + } + } + } + pr_debug("_i2c_entry_get %p %p\n", adap, entry); + return entry; +} + +struct i2c_op_q_entry *i2c_entry_get(struct i2c_adapter * adap) +{ + unsigned long flags; + struct i2c_op_q_entry * entry; + + spin_lock_irqsave(&adap->q_lock, flags); + entry = _i2c_entry_get(adap); + spin_unlock_irqrestore(&adap->q_lock, flags); + return entry; +} + +void i2c_entry_put(struct i2c_adapter * adap, + struct i2c_op_q_entry * entry) +{ + unsigned long flags; + struct i2c_op_q_entry * new_entry = NULL; + + restart: + pr_debug("i2c_put %p %p\n", adap, entry); + /* Subtle reasons why we don't need a lock before the dec, see + the get routine for more details. */ + if (atomic_dec_and_test(&entry->usecount)) { + spin_lock_irqsave(&adap->q_lock, flags); + list_del(&entry->link); + + /* Get the next entry to start. */ + new_entry = _i2c_entry_get(adap); + spin_unlock_irqrestore(&adap->q_lock, flags); + + entry->handler(entry); + + if (new_entry) { + /* start entry will go here. */ + if (new_entry->start) + complete(new_entry->start); + /* Do tail recursion ourself. */ + entry = new_entry; + goto restart; + } + } +} + +void i2c_op_done(struct i2c_adapter *adap, struct i2c_op_q_entry *e) +{ + pr_debug("i2c_op_done: %p %p\n", adap, e); + if (atomic_dec_and_test(&e->completed)) { + /* We are the lucky winner! We get to clean up the + entry. */ + if (e->complete) + e->complete(adap, e); + } + + i2c_entry_put(adap, e); +} + EXPORT_SYMBOL(i2c_add_adapter); EXPORT_SYMBOL(i2c_del_adapter); EXPORT_SYMBOL(i2c_add_driver); @@ -1345,6 +1443,7 @@ EXPORT_SYMBOL(i2c_clients_command); EXPORT_SYMBOL(i2c_check_addr); +EXPORT_SYMBOL(i2c_op_done); EXPORT_SYMBOL(i2c_master_send); EXPORT_SYMBOL(i2c_master_recv); EXPORT_SYMBOL(i2c_control); Index: linux-2.6.11-rc4/include/linux/i2c.h =================================================================== --- linux-2.6.11-rc4.orig/include/linux/i2c.h +++ linux-2.6.11-rc4/include/linux/i2c.h @@ -33,6 +33,8 @@ #include #include /* for struct device */ #include +#include +#include #include #include @@ -184,6 +186,33 @@ } /* + * About locking and the non-blocking interface. + * + * The poll operations are called single-threaded (along with the + * xxx_start operations), so if the driver is only polled then there + * is no need to do any locking. If you are using interrupts, then + * the timer operations and interrupts can race and you need to lock + * appropriately. + * + * i2c_op_done() can be called multiple times on the same entry (as + * long as each one has a get operation). This handles poll and + * interrupt races calling i2c_op_done(). It will do the right thing. + */ + +/* Called from an non-blocking interface to get the current working + entry. Returns NULL if there is none. This is primarily for + interrupt handlers to determine what they should be working on. + Note that if you call i2c_entry_get() and get a non-null entry, you + must call i2c_entry_put() on it. */ +struct i2c_op_q_entry *i2c_entry_get(struct i2c_adapter * adap); +void i2c_entry_put(struct i2c_adapter * adap, + struct i2c_op_q_entry * entry); + +/* Called from an non-blocking interface to report that an operation + has completed. Can be called from interrupt context. */ +void i2c_op_done(struct i2c_adapter *adap, struct i2c_op_q_entry *entry); + +/* * The following structs are for those who like to implement new bus drivers: * i2c_algorithm is the interface to a class of hardware solutions which can * be addressed using the same bus algorithms - i.e. bit-banging or the PCF8584 @@ -231,6 +260,9 @@ int (*client_unregister)(struct i2c_client *); /* data fields that are valid for all devices */ + struct list_head q; + spinlock_t q_lock; + struct semaphore bus_lock; int timeout; --------------030405070502080907060108--