linux-kernel - Re: [PATCH 1/3] sysfs: Fix is_visible() support for binary attributes

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Date:	Tue, 8 Sep 2015 12:10:02 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	Guenter Roeck <linux@...ck-us.net>
Cc:	Emilio López <emilio.lopez@...labora.co.uk>,
	olof@...om.net, kgene@...nel.org, k.kozlowski@...sung.com,
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-samsung-soc@...r.kernel.org
Subject: Re: [PATCH 1/3] sysfs: Fix is_visible() support for binary attributes

On Tue, Sep 08, 2015 at 08:30:13AM -0700, Guenter Roeck wrote:
> Emilio,
> 
> On Tue, Sep 08, 2015 at 09:07:44AM -0300, Emilio López wrote:
> > According to the sysfs header file:
> > 
> >     "The returned value will replace static permissions defined in
> >      struct attribute or struct bin_attribute."
> > 
> > but this isn't the case, as is_visible is only called on
> > struct attribute only. This patch adds the code paths required
> > to support is_visible() on binary attributes.
> > 
> > Signed-off-by: Emilio López <emilio.lopez@...labora.co.uk>
> > ---
> >  fs/sysfs/group.c | 22 ++++++++++++++++++----
> >  1 file changed, 18 insertions(+), 4 deletions(-)
> > 
> > diff --git a/fs/sysfs/group.c b/fs/sysfs/group.c
> > index 39a0199..eb6996a 100644
> > --- a/fs/sysfs/group.c
> > +++ b/fs/sysfs/group.c
> > @@ -37,10 +37,10 @@ static int create_files(struct kernfs_node *parent, struct kobject *kobj,
> >  {
> >  	struct attribute *const *attr;
> >  	struct bin_attribute *const *bin_attr;
> > -	int error = 0, i;
> > +	int error = 0, i = 0;
> >  
> >  	if (grp->attrs) {
> > -		for (i = 0, attr = grp->attrs; *attr && !error; i++, attr++) {
> > +		for (attr = grp->attrs; *attr && !error; i++, attr++) {
> >  			umode_t mode = (*attr)->mode;
> >  
> >  			/*
> > @@ -73,13 +73,27 @@ static int create_files(struct kernfs_node *parent, struct kobject *kobj,
> >  	}
> >  
> >  	if (grp->bin_attrs) {
> > -		for (bin_attr = grp->bin_attrs; *bin_attr; bin_attr++) {
> > +		for (bin_attr = grp->bin_attrs; *bin_attr; i++, bin_attr++) {
> > +			umode_t mode = (*bin_attr)->attr.mode;
> > +
> >  			if (update)
> >  				kernfs_remove_by_name(parent,
> >  						(*bin_attr)->attr.name);
> > +			if (grp->is_visible) {
> > +				mode = grp->is_visible(kobj,
> > +						       &(*bin_attr)->attr, i);
> 
> With this, if 'n' is the number of non-binary attributes,
> 
> for i < n:
> 	The index passed to is_visible points to a non-binary attribute.
> for i >= n:
> 	The index passed to is_visible points to the (index - n)th binary
> 	attribute.
> 
> Unless I am missing something, this is not explained anywhere, but it is
> not entirely trivial to understand. I think it should be documented.

I agree, make i the number of the bin attribute and that should solve
this issue.

thanks,

greg k-h
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