On Wed, Sep 25, 2013 at 10:20:35PM +0200, Wolfram Sang wrote: > On Sat, Aug 31, 2013 at 09:30:19AM -0700, Guenter Roeck wrote: > > The 'name' attribute is needed for all i2c-dev class devices, meaning > > it can be created automatically by pointing to it in the class data > > structure. This simplifies the code and reduces the probability for race > > conditions. > > What race condition? >
Userspace trying to access the name attribute before it is created. See http://kroah.com/log/blog/2013/06/26/how-to-create-a-sysfs-file-correctly/ for details; Greg describes the problem and solution much better than I could ever do. > > > > Signed-off-by: Guenter Roeck <[email protected]> > > --- > > drivers/i2c/i2c-dev.c | 32 ++++++++++++++++---------------- > > 1 file changed, 16 insertions(+), 16 deletions(-) > > > > diff --git a/drivers/i2c/i2c-dev.c b/drivers/i2c/i2c-dev.c > > index c3ccdea..46eea02 100644 > > --- a/drivers/i2c/i2c-dev.c > > +++ b/drivers/i2c/i2c-dev.c > > @@ -111,7 +111,11 @@ static ssize_t show_adapter_name(struct device *dev, > > return -ENODEV; > > return sprintf(buf, "%s\n", i2c_dev->adap->name); > > } > > -static DEVICE_ATTR(name, S_IRUGO, show_adapter_name, NULL); > > + > > +static struct device_attribute i2c_dev_attributes[] = { > > + __ATTR(name, S_IRUGO, show_adapter_name, NULL), > > + { } > > +}; > > > > /* > > ------------------------------------------------------------------------- */ > > > > @@ -538,7 +542,11 @@ static const struct file_operations i2cdev_fops = { > > > > /* > > ------------------------------------------------------------------------- */ > > > > -static struct class *i2c_dev_class; > > +static struct class i2c_dev_class = { > > + .owner = THIS_MODULE, > > + .name = "i2c-dev", > > + .dev_attrs = i2c_dev_attributes, > > +}; > > Have you tried this with two instances? I don't think it will work since > class_register modifies the class struct. > Half a dozen instances, actually. Unless I am missing something, seems to be unlikely that there is a problem, since the kernel would fail all over the place if there was a problem with class->dev_attrs (or its replacement dev_groups); Anyway, the patch is obsolete; one is supposed to use class->dev_groups now. Thanks, Guenter -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
