Re: [PATCH v6 3/4] of: overlay: add per overlay sysfs attributes

[Pantelis Antoniou <pantelis.antoniou@konsulko.com>]

Hi Greg,

> On Oct 21, 2015, at 00:08 , Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote:
> 
> On Tue, Oct 20, 2015 at 10:13:16PM +0300, Pantelis Antoniou wrote:
>> * A per overlay can_remove sysfs attribute that reports whether
>> the overlay can be removed or not due to another overlapping overlay.
>> 
>> * A target sysfs attribute listing the target of each fragment,
>> in a group named after the name of the fragment.
>> 
>> Signed-off-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
>> ---
>> drivers/of/overlay.c | 103 +++++++++++++++++++++++++++++++++++++++++++++++++--
>> 1 file changed, 99 insertions(+), 4 deletions(-)
>> 
>> diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
>> index 067404e..2d51d9e2 100644
>> --- a/drivers/of/overlay.c
>> +++ b/drivers/of/overlay.c
>> @@ -25,8 +25,23 @@
>> 
>> #include "of_private.h"
>> 
>> +/* fwd. decl */
>> +struct of_overlay;
>> +struct of_overlay_info;
>> +
>> +/* an attribute for each fragment */
>> +struct fragment_attribute {
>> +	struct attribute attr;
>> +	ssize_t (*show)(struct kobject *kobj, struct fragment_attribute *fattr,
>> +			char *buf);
>> +	ssize_t (*store)(struct kobject *kobj, struct fragment_attribute *fattr,
>> +			 const char *buf, size_t count);
>> +	struct of_overlay_info *ovinfo;
>> +};
>> +
>> /**
>>  * struct of_overlay_info - Holds a single overlay info
>> + * @info:	info node that contains the target and overlay
>>  * @target:	target of the overlay operation
>>  * @overlay:	pointer to the overlay contents node
>>  *
>> @@ -34,8 +49,13 @@
>>  * records.
>>  */
>> struct of_overlay_info {
>> +	struct of_overlay *ov;
>> +	struct device_node *info;
>> 	struct device_node *target;
>> 	struct device_node *overlay;
>> +	struct attribute_group attr_group;
>> +	struct attribute *attrs[2];
> 
> Why both 2 attributes _and_ an attribute group?  Why not put the
> attributes in the attribute group?
> 
> And why just one attribute group?  Why not an array of them like the
> rest of the kernel is used to handle?
> 

Because this makes it easier to add all the attributes for all the fragments in a single
sysfs_create_groups() call, once for each overlay, instead of having a call to 
sysfs_create_group() for each fragment of the overlay.

Reusing driver core helpers is good, no?

> thanks,
> 
> greg k-h

Regards

— Pantelis