On Mon, Feb 23, 2015 at 05:51:22PM +0100, Lukasz Majewski wrote:

Hi Guenter,

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On Mon, Feb 23, 2015 at 05:13:36PM +0100, Lukasz Majewski wrote:

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Hi Guenter,

[ ... ]

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If devicetree is not configured, of_property_count_elems_of_size
returns -ENOSYS, which is returned, causing the driver to fail
loading.

Has of_property_count_elems_of_size() returns -ENOSYS?

Maybe something has changed, but in my linux-vanila (3.19-rc4)
at ./drivers/of/base.c it returns -EINVAL, -ENODATA or number of
elements.

Have I missed something?

Hi Lukasz,

Yes, you have. Check include/linux/of.h, line 484, in latest mainline.

Ok. Now I got it.

The above situation shouldn't happen if I put of_find_property() check
on the very beginning of this function (it returns NULL when DT support
is not compiled).

Correct.

The function would look as follows:

int 
pwm_fan_of_get_cooling_data(struct device *dev, struct pwm_fan_ctx
*ctx) 
{       
        struct device_node *np = dev->of_node;
	int num, i, ret;

	if (!of_find_property(np, "cooling-levels", NULL))
		return 0;

	ret = of_property_count_u32_elems(np, "cooling-levels");
	if (ret <= 0) {
		dev_err(dev, "Wrong data!\n");
		return ret;

This should probably be something like 

		return ret ? : -EINVAL;

or ret == 0 is not an error, and you should not display an error message
in that case.

Thanks,
Guenter