linux-kernel - Re: [PATCH 14/34] sysfs, kernfs: prepare read path for kernfs

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Message-ID: <20131027113020.GD14934@mtj.dyndns.org>
Date:	Sun, 27 Oct 2013 07:30:20 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Pavel Machek <pavel@....cz>
Cc:	gregkh@...uxfoundation.org, kay@...y.org,
	linux-kernel@...r.kernel.org, ebiederm@...ssion.com,
	bhelgaas@...gle.com
Subject: Re: [PATCH 14/34] sysfs, kernfs: prepare read path for kernfs

On Sat, Oct 26, 2013 at 01:32:21PM +0200, Pavel Machek wrote:
> Hi!
> 
> > We're in the process of separating out core sysfs functionality into
> > kernfs which will deal with sysfs_dirents directly.  This patch
> > rearranges read path so that the kernfs and sysfs parts are separate.
> 
> > +static int sysfs_kf_seq_show(struct seq_file *sf, void *v)
> >  {
> >  	struct sysfs_open_file *of = sf->private;
> >  	struct kobject *kobj = of->sd->s_parent->priv;
> > -	const struct sysfs_ops *ops;
> > +	const struct sysfs_ops *ops = sysfs_file_ops(of->sd);
> > +	ssize_t count = 0;
> >  	char *buf;
> > -	ssize_t count;
> >  
> >  	/* acquire buffer and ensure that it's >= PAGE_SIZE */
> >  	count = seq_get_buf(sf, &buf);
> 
> Initing count to zero is superfluous here.

Ooh, right.

> > +	/* the same behavior as single_open() */
> > +	return NULL + !*ppos;
> > +}
> 
> That's certainly interesting code.

Directly copied from single_*() functions.  Will add some comments but
what it's doing is inherently slightly tricky.

Thanks.

-- 
tejun
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