Re: [PATCH v3] ASoC: Remove 'const' from the device_node pointers
From: Lars-Peter Clausen
Date: Tue Nov 25 2014 - 08:36:21 EST
On 11/25/2014 02:13 PM, Mark Brown wrote:
On Tue, Nov 25, 2014 at 12:14:48PM +0100, Jean-Francois Moine wrote:
As Russell King's explained it, there should not be pointers to
struct device_node:
"struct device_node is a ref-counted structure. That means if you
store a reference to it, you should "get" it, and you should "put"
it once you've done. The act of "put"ing the pointed-to structure
involves writing to that structure, so it is totally unappropriate
to store a device_node structure as a const pointer. It forces you
to have to cast it back to a non-const pointer at various points
in time to use various OF function calls."
So, we're not holding references here (we're just doing comparisons, the
references need to be owned before we get into the core)
The core itself will only do the comparisons and it is the board drivers
responsibility to get and put the references. Making the pointers non const
allows the board driver to use them to put the reference once the card has
been unregistered rather than having to keep a separate set of pointers
around. This should probably be mentioned in the commit message though.
I'm not seeing anything here removing casts?
This patch used to be part of a two part series where the second patch
removed the casts. This patch as already been applied though.
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