linux-kernel - Re: [PATCH] clk: core: Copy connection id

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Message-ID: <20170228080558.GL25384@codeaurora.org>
Date:   Tue, 28 Feb 2017 00:05:58 -0800
From:   "sboyd@...eaurora.org" <sboyd@...eaurora.org>
To:     Leonard Crestez <leonard.crestez@....com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "mturquette@...libre.com" <mturquette@...libre.com>,
        "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>
Subject: Re: [PATCH] clk: core: Copy connection id

On 02/25, Leonard Crestez wrote:
> On Fri, 2017-02-24 at 12:44 -0800, Stephen Boyd wrote:
> > On 02/20, Leonard Crestez wrote:
> > > Some drivers use sprintf to build clk connection id names but the
> > > clk
> > > core will save those strings and occasionally print them back.
> > > Duplicate
> > > the con_id strings instead of fixing all the users.
> > 
> > Good catch. What about dev_id though? That could also have the
> > same problem if some device is removed and we're still holding a
> > reference to the kobject's name. This is probably more rare than
> > what is happening here, but still seems possible that we might
> > trip over that later.
> 
> A device should normally free the clks it uses before it is destroyed.
> This means that if dev_id is pointing to freed memory then the clk
> itself was probably leaked, right?

Sure. clk_get_sys() could be called and then we could have
something sprintf the dev_id there. A quick grep doesn't show any
place where that happens though so it seems safe right now.

That said, it would be nice to clearly document that we don't
expect dev_id to be freed or changed during the lifetime of the
clk structure, but we do allow con_id to change. Perhaps the copy
shows that, but a comment would also be useful so we don't have
people wondering why dev_id isn't copied as well.

> 
> This is obvious misuse of the API, not like sprintf-ing a con_id in a
> complex driver. I don't really think it's worth copying strings for it.
> 

Ok.

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