Replacing deprecated "dev_attrs" attribute with "dev_groups"

Question

I'm trying to compile a Linux device driver (kernel module), however the module was last updated in April 2013 and of course it doesn't compile anymore on a recent (3.13) kernel, here's the error :

als_sys.c:99:2: error: unknown field ‘dev_attrs’ specified in initializer

I've searched already but all that I found were patches, there is no clear "tutorial" about updating an old module, the only thing I understood was that I need to use dev_groups instead, but it doesn't accept the same value as dev_attrs and I don't know how to adapt the existing code for that.

The code (some of it, the entire code can be found here) :

# als_sys.c

static ssize_t
illuminance_show(struct device *dev, struct device_attribute *attr, char *buf)
{
    struct als_device *als = to_als_device(dev);
    int illuminance;
    int result;

    result = als->ops->get_illuminance(als, &illuminance);
    if (result)
        return result;

    if (!illuminance)
        return sprintf(buf, "0\n");
    else if (illuminance == -1)
        return sprintf(buf, "-1\n");
    else if (illuminance < -1)
        return -ERANGE;
    else
        return sprintf(buf, "%d\n", illuminance);
}

# truncated - also "adjustment_show" is similar to this function so
# I didn't copy/paste it to save some space in the question

static struct device_attribute als_attrs[] = { # that's what I need to modify, but
    __ATTR(illuminance, 0444, illuminance_show, NULL), # I have no clue what to
    __ATTR(display_adjustment, 0444, adjustment_show, NULL), # put here instead
    __ATTR_NULL,
};

# truncated

static struct class als_class = {
    .name = "als",
    .dev_release = als_release,
    .dev_attrs = als_attrs, # line 99, that's where it fails
};

EDIT

As mentioned in the answer below, I changed the code like this :

static struct device_attribute als_attrs[] = {
    __ATTR(illuminance, 0444, illuminance_show, NULL),
    __ATTR(display_adjustment, 0444, adjustment_show, NULL),
    __ATTR_NULL,
};

static const struct attribute_group als_attr_group = {
    .attrs = als_attrs,
};

static struct class als_class = {
    .name = "als",
    .dev_release = als_release,
    .dev_groups = als_attr_group, # line 103 - it fails here again
};

But I still get another error :

als_sys.c:103:2: error: initializer element is not constant

I've found this question which is about the same error however its answer is about a single attribute and I don't know how to adapt it for multiple ones.

Thanks for your help and have a nice day.

score 5 · Accepted Answer · edited May 23 '17 at 12:23

5

Indeed, dev_attrs was replaced with dev_groups in 3.13. In 3.12 they were both presented in struct. Look at 3.12 version and 3.13 version.

Anyway, there should not be a problem, because simple search for attribute_group gives you a lot of examples.

Simply put, you have to embed your dev_attrs inside dev_group:

static const struct attribute_group als_attr_group = {
        .attrs = als_attrs,
};

And then use that attribute group in struct class.

There is also a handy macro ATTRIBUTE_GROUPS. See example usage https://lkml.org/lkml/2013/10/23/218.

EDIT:

Remove const declaration from attribute group like this:

static struct attribute_group als_attr_group = {
        .attrs = als_attrs,
};

Because you can't initialize const struct with something that is not literal like 0xff or 'c'. See more detailes here.

edited May 23 '17 at 12:23

Community

1
1

answered Feb 19 '14 at 07:19

Alexander Dzyoba

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Thanks but your solution gives me another error, please look at my edited question. – Feb 19 '14 at 14:54
Actually, `const` or not makes no difference, exact same error at the exact same line. – Feb 19 '14 at 19:15
Well, I can keep guessing what thing you should tinker to avoid compilation error, but it starts to be off-topic regarding to your original question. – Alexander Dzyoba Feb 19 '14 at 19:15
Ok thanks anyway, I'll post that as a separate question. – Feb 19 '14 at 19:16

Replacing deprecated "dev_attrs" attribute with "dev_groups"

1 Answers1