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LKML: Greg KH: [PATCH] I2C: pcf8574 doesn't need a lock
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It<br />uses a lock where it's not needed.<br /><br />While we were there, we did some additional cleanups to the driver:<br />1* Merge pcf8574_update_client() in show_read(), as it was the only user<br />and the function became trivial once the locking was removed.<br />2* Add a validity check on values provided by user-space.<br /><br />Aurelien Jarno tested the modified code for confirmation and it worked<br />just fine.<br /><br />Signed-off-by: Jean Delvare <khali@linux-fr.org><br />Signed-off-by: Aurelien Jarno <aurelien@aurel32.net><br />Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de><br /><br /><br /> drivers/i2c/chips/pcf8574.c | 27 +++++++++------------------<br /> 1 files changed, 9 insertions(+), 18 deletions(-)<br /><br /><br />diff -Nru a/drivers/i2c/chips/pcf8574.c b/drivers/i2c/chips/pcf8574.c<br />--- a/drivers/i2c/chips/pcf8574.c 2005-04-01 11:53:38 -08:00<br />+++ b/drivers/i2c/chips/pcf8574.c 2005-04-01 11:53:38 -08:00<br />@@ -56,7 +56,6 @@<br /> /* Each client has this additional data */<br /> struct pcf8574_data {<br /> struct i2c_client client;<br />- struct semaphore update_lock;<br /> <br /> u8 read, write; /* Register values */<br /> };<br />@@ -65,7 +64,6 @@<br /> static int pcf8574_detect(struct i2c_adapter *adapter, int address, int kind);<br /> static int pcf8574_detach_client(struct i2c_client *client);<br /> static void pcf8574_init_client(struct i2c_client *client);<br />-static struct pcf8574_data *pcf8574_update_client(struct device *dev);<br /> <br /> /* This is the driver that will be inserted */<br /> static struct i2c_driver pcf8574_driver = {<br />@@ -80,7 +78,9 @@<br /> /* following are the sysfs callback functions */<br /> static ssize_t show_read(struct device *dev, char *buf)<br /> {<br />- struct pcf8574_data *data = pcf8574_update_client(dev);<br />+ struct i2c_client *client = to_i2c_client(dev);<br />+ struct pcf8574_data *data = i2c_get_clientdata(client);<br />+ data->read = i2c_smbus_read_byte(client); <br /> return sprintf(buf, "%u\n", data->read);<br /> }<br /> <br />@@ -97,7 +97,12 @@<br /> {<br /> struct i2c_client *client = to_i2c_client(dev);<br /> struct pcf8574_data *data = i2c_get_clientdata(client);<br />- data->write = simple_strtoul(buf, NULL, 10);<br />+ unsigned long val = simple_strtoul(buf, NULL, 10);<br />+<br />+ if (val > 0xff)<br />+ return -EINVAL;<br />+<br />+ data->write = val;<br /> i2c_smbus_write_byte(client, data->write);<br /> return count;<br /> }<br />@@ -157,7 +162,6 @@<br /> <br /> /* Fill in the remaining client fields and put it into the global list */<br /> strlcpy(new_client->name, client_name, I2C_NAME_SIZE);<br />- init_MUTEX(&data->update_lock);<br /> <br /> /* Tell the I2C layer a new client has arrived */<br /> if ((err = i2c_attach_client(new_client)))<br />@@ -200,19 +204,6 @@<br /> struct pcf8574_data *data = i2c_get_clientdata(client);<br /> data->write = PCF8574_INIT;<br /> i2c_smbus_write_byte(client, data->write);<br />-}<br />-<br />-static struct pcf8574_data *pcf8574_update_client(struct device *dev)<br />-{<br />- struct i2c_client *client = to_i2c_client(dev);<br />- struct pcf8574_data *data = i2c_get_clientdata(client);<br />-<br />- down(&data->update_lock);<br />- dev_dbg(&client->dev, "Starting pcf8574 update\n");<br />- data->read = i2c_smbus_read_byte(client); <br />- up(&data->update_lock);<br />- <br />- return data;<br /> }<br /> <br /> static int __init pcf8574_init(void)<br />-<br />To unsubscribe from this list: send the line "unsubscribe linux-kernel" in<br />the body of a message to majordomo@vger.kernel.org<br />More majordomo info at <a href="http://vger.kernel.org/majordomo-info.html">http://vger.kernel.org/majordomo-info.html</a><br />Please read the FAQ at <a href="http://www.tux.org/lkml/">http://www.tux.org/lkml/</a><br /><br /></pre></td><td width="32" rowspan="2" class="c" valign="top"><img src="/images/icornerr.gif" width="32" height="32" alt="\" /></td></tr><tr><td align="right" valign="bottom"> 聽 </td></tr><tr><td align="right" valign="bottom">聽</td><td class="c" valign="bottom" style="padding-bottom: 0px"><img src="/images/bcornerl.gif" width="32" height="32" alt="\" /></td><td class="c">聽</td><td class="c" valign="bottom" style="padding-bottom: 0px"><img src="/images/bcornerr.gif" width="32" height="32" alt="/" /></td></tr><tr><td align="right" valign="top" colspan="2"> 聽 </td><td class="lm">Last update: 2005-04-06 13:31 聽聽 [from the cache]<br />漏2003-2020 <a href="http://blog.jasper.es/"><span itemprop="editor">Jasper Spaans</span></a>|hosted at <a href="https://www.digitalocean.com/?refcode=9a8e99d24cf9">Digital Ocean</a> and my Meterkast|<a href="http://blog.jasper.es/categories.html#lkml-ref">Read the blog</a></td><td>聽</td></tr></table><script language="javascript" src="/js/styleswitcher.js" type="text/javascript"></script></body></html>