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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:
    > 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.

    --
    Russell King
    Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/
    maintainer of: 2.6 Serial core
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