linux-kernel - Re: [PATCH 2/7] mfd / platform: cros_ec: move lightbar attributes to its own driver.

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Date:   Fri, 23 Nov 2018 12:52:55 +0100
From:   Enric Balletbo i Serra <enric.balletbo@...labora.com>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     lee.jones@...aro.org, gwendal@...omium.org, drinkcat@...omium.org,
        linux-kernel@...r.kernel.org, groeck@...omium.org,
        kernel@...labora.com, bleung@...omium.org,
        Olof Johansson <olof@...om.net>
Subject: Re: [PATCH 2/7] mfd / platform: cros_ec: move lightbar attributes to
 its own driver.

Hi Guenter,

On 22/11/18 18:41, Guenter Roeck wrote:
> Hi Enric,
> 
> On Thu, Nov 22, 2018 at 12:33:51PM +0100, Enric Balletbo i Serra wrote:
>> The entire way how cros sysfs attibutes are created is broken.
>> cros_ec_lightbar should be its own driver and its attributes should be
>> associated with a lightbar driver not the mfd driver. In order to retain
>> the path, the lightbar attributes are attached to the cros_class.
>>
>> The patch also adds the sysfs documentation.
>>
>> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@...labora.com>
>> ---
>>
> ...
>>  
>> +int cros_ec_attach_attribute_group(struct cros_ec_dev *ec,
>> +				   struct attribute_group *attrs)
>> +{
>> +	return sysfs_create_group(&ec->class_dev.kobj, attrs);
>> +}
>> +EXPORT_SYMBOL(cros_ec_attach_attribute_group);
>> +
>> +void cros_ec_detach_attribute_group(struct cros_ec_dev *ec,
>> +				    struct attribute_group *attrs)
>> +{
>> +	sysfs_remove_group(&ec->class_dev.kobj, attrs);
>> +}
>> +EXPORT_SYMBOL(cros_ec_detach_attribute_group);
>> +
> 
> Are those two functions necessary ? Why not just call sysfs_create_group
> and sysfs_remove_group directly from the calling code ?
> 

Actually we have cros_ec_dev which registers the cros_ec class, and sysfs/vbc
and lightbar using this cros_ec class. I had problems unloading the different
modules. For example, when I removed cros_ec_dev modules before
cros_ec_sysfs/cros_ec_vbc/cros_ec_lightbar I got a hang.

To solve the hang I did the easy solution that is make these drivers depend on
cros_ec_dev so you're not able to unload cros_ec_dev if first you don't unload
the sysfs/vbc/lightbar.

Thinking again about it, I don't really understand now why failed in the first
place, cros_ec_dev is the parent, so, on remove should call mfd_remove_devices
for the subdevices.

So, let me check again this and I'll back to you.

Thanks,
 Enric


> Thanks,
> Guenter
>