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SubjectRe: [PATCH 2.6.12-rc4 1/12] (dynamic sysfs callbacks) update device attribute callbacks
On Sat, May 14, 2005 at 03:46:31PM -0400, Yani Ioannou wrote:
> My first post to LKML on the patch:
> 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.

Russell King
Linux kernel 2.6 ARM Linux -
maintainer of: 2.6 Serial core
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