linux-kernel - Re: [PATCH RESEND 6/6] clk: s5p-g2d: Fix incorrect usage of IS_ERR_OR

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Message-ID: <20130103100000.GJ2631@n2100.arm.linux.org.uk>
Date:	Thu, 3 Jan 2013 10:00:01 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Dan Carpenter <dan.carpenter@...cle.com>
Cc:	Tony Prisk <linux@...sktech.co.nz>,
	Tomasz Stanislawski <t.stanislaws@...sung.com>,
	Dan Carpenter <error27@...il.com>,
	Sergei Shtylyov <sshtylyov@...sta.com>,
	kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Sylwester Nawrocki <sylvester.nawrocki@...il.com>,
	linux-arm-kernel@...ts.infradead.org, linux-media@...r.kernel.org
Subject: Re: [PATCH RESEND 6/6] clk: s5p-g2d: Fix incorrect usage of
	IS_ERR_OR_NULL

On Thu, Jan 03, 2013 at 12:05:20PM +0300, Dan Carpenter wrote:
> On Wed, Jan 02, 2013 at 06:31:53PM +1300, Tony Prisk wrote:
> > Why should a _consumer_ of a clock care?  It is _very_ important that
> > people get this idea - to a consumer, the struct clk is just an opaque
> > cookie.  The fact that it appears to be a pointer does _not_ mean that
> > the driver can do any kind of dereferencing on that pointer - it should
> > never do so.
> > 
> > Thread can be viewed here:
> > https://lkml.org/lkml/2012/12/20/105
> > 
> 
> Ah.  Grand.  Thanks...
> 
> Btw. The documentation for clk_get() really should include some of
> this information.

It *does* contain this information.  The problem is that driver authors
_ARE_ stupid, lazy morons who don't bother to read documentation.

/**
 * clk_get - lookup and obtain a reference to a clock producer.
 * @dev: device for clock "consumer"
 * @id: clock consumer ID
 *
 * Returns a struct clk corresponding to the clock producer, or
 * valid IS_ERR() condition containing errno.  The implementation
 * uses @dev and @id to determine the clock consumer, and thereby
 * the clock producer.  (IOW, @id may be identical strings, but
 * clk_get may return different clock producers depending on @dev.)
 *
 * Drivers must assume that the clock source is not enabled.
 *
 * clk_get should not be called from within interrupt context.
 */

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