Re: [PATCH 2.6.12-rc4 1/12] (dynamic sysfs callbacks) update device attribute callbacks

[Greg KH]

On Sat, May 14, 2005 at 10:18:38PM +0100, Russell King wrote:
> On Sat, May 14, 2005 at 03:46:31PM -0400, Yani Ioannou wrote:
> > My first post to LKML on the patch:
> > http://lkml.org/lkml/2005/5/7/60
> > 
> > The idea originated in the lm_sensors mailing list, so you might want
> > to take a look at the lm_sensors archive is you are interested, in
> > particular the following thread:
> > ...
> > 
> > This isn't changing, although there are cases where it is
> > necessary/preferable to dynamically create the attributes (again see
> > previous discussion). This patch helps both static and dynamically
> > created attributes. The adm1026 example I posted to the mailing list
> > earlier uses entirely static attributes still (and hence the need for
> > the new macros my latest patch adds), and I expect most attributes
> > will remain static.
> 
> Ok.  I do wonder if the better solution would be to encapsulate
> "device_attribute" where this extra information is required, and
> pass a pointer to device_attribute to its methods, in much the
> same way as "sysfs_ops" works.
> 
> This means your attributes in adm1016 become:
> 
> struct adm1016_attr {
> 	struct device_attribute	dev_attr;
> 	int			nr;
> };
> 
> #define ADM1016_ATTR(_name,_mode,_show,_store,_nr)		\
> 	struct adm1016_attr adm_attr_##_name = {		\
> 		.dev_attr = __ATTR(_name,_mode,_show,_store),	\
> 		.nr = _nr,					\
> 	}
> 
> static ssize_t show_temp_max(struct device *dev, struct device_attribute *attr, char *buf)
> {
> 	struct adm1016_attr *adm_attr = to_adm_attr(attr);
> 	struct adm1026_data *data = adm1026_update_device(dev);
> 	return sprintf(buf,"%d\n", TEMP_FROM_REG(data->temp_max[adm_attr->nr]));
> }
> 
> #define temp_reg(offset)					\
> ...
> static ADM1016_ATTR(temp##offset##_max, S_IRUGO | S_IWUSR,	\
> 	show_temp_max, set_temp_max, offset)
> 
> There are two advantages to this way:
> 
> 1. you're not having to impose the extra void * pointer in the
>    attribute on everyone.
> 2. you allow people to add whatever data they please to the attribute
>    in whatever format they wish - whether it be a void pointer, integer,
>    or whatever.
> 
> This seems far more flexible to me, at least.

Ah, nice, I hadn't thought about that.  But yes, it would be much
smaller and simpler to do this, very good idea.

And if enough i2c drivers want to do this, just make a i2c driver
attribute that they all use to achieve this.

Yani, what do you think?

thanks,

greg k-h
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