| Message ID | d5d74f6993e9f2392008a27a2938c58d47dc8062.1415562021.git.moinejf@free.fr (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | c362effe5cda4df02aa7670d58636ea73979e304 |
| Headers | show |
On Sun, Nov 09, 2014 at 08:33:45PM +0100, Jean-Francois Moine wrote: > From Russell King: > of_node_put() modifies the struct device_node contents. Therefore, > of_node_put() definitely not treating the data pointed to as read-only, > and therefore it is completely inappropriate for it to be marked "const". Did Russell write this patch (in which case it's missing a signoff and his e-mail address above) or are you trying to say "Russell King said..."?
On Mon, 10 Nov 2014 19:03:32 +0000 Mark Brown <broonie@kernel.org> wrote: > On Sun, Nov 09, 2014 at 08:33:45PM +0100, Jean-Francois Moine wrote: > > From Russell King: > > of_node_put() modifies the struct device_node contents. Therefore, > > of_node_put() definitely not treating the data pointed to as read-only, > > and therefore it is completely inappropriate for it to be marked "const". > > Did Russell write this patch (in which case it's missing a signoff and > his e-mail address above) or are you trying to say "Russell King > said..."? Sorry, that was "Russell said ...". Do you want I resubmit the patch?
On Mon, Nov 10, 2014 at 08:12:54PM +0100, Jean-Francois Moine wrote: > Mark Brown <broonie@kernel.org> wrote: > > Did Russell write this patch (in which case it's missing a signoff and > > his e-mail address above) or are you trying to say "Russell King > > said..."? > Sorry, that was "Russell said ...". > Do you want I resubmit the patch? Let me look at the change, I didn't do that yet (what you wrote looks awfully like the patch submission format for sending code someone else wrote...).
On Sun, Nov 09, 2014 at 08:33:45PM +0100, Jean-Francois Moine wrote: > index 7ba7130..405f967 100644 > --- a/include/sound/soc.h > +++ b/include/sound/soc.h > @@ -886,7 +886,7 @@ struct snd_soc_platform_driver { > > struct snd_soc_dai_link_component { > const char *name; > - const struct device_node *of_node; > + struct device_node *of_node; > const char *dai_name; > }; > The changelog talked about of_node_put() but I'm not seeing anything in the code which calls that except snd_soc_of_get_dai_name()? Everything else just does comparisons of the pointer AFIACT from a quick scan through.
On Mon, Nov 10, 2014 at 07:37:04PM +0000, Mark Brown wrote: > On Sun, Nov 09, 2014 at 08:33:45PM +0100, Jean-Francois Moine wrote: > > > index 7ba7130..405f967 100644 > > --- a/include/sound/soc.h > > +++ b/include/sound/soc.h > > @@ -886,7 +886,7 @@ struct snd_soc_platform_driver { > > > > struct snd_soc_dai_link_component { > > const char *name; > > - const struct device_node *of_node; > > + struct device_node *of_node; > > const char *dai_name; > > }; > > > > The changelog talked about of_node_put() but I'm not seeing anything in > the code which calls that except snd_soc_of_get_dai_name()? Everything > else just does comparisons of the pointer AFIACT from a quick scan > through. I think it comes from these files (from a previous patch from Jean adding a load of inappropriate const's to places where they do not belong): sound/soc/generic/simple-card.c | 7 ++----- sound/soc/samsung/odroidx2_max98090.c | 4 ++-- sound/soc/ux500/mop500.c | 6 ++---- That patch was trying to do this to those three files: - np = (struct device_node *) dai_link->cpu_of_node; - of_node_put(np); - np = (struct device_node *) dai_link->codec_of_node; - of_node_put(np); + of_node_put(dai_link->cpu_of_node); + of_node_put(dai_link->codec_of_node); ... - of_node_put((struct device_node *)odroidx2_dai[0].cpu_of_node); - of_node_put((struct device_node *)odroidx2_dai[0].codec_of_node); + of_node_put(odroidx2_dai[0].cpu_of_node); + of_node_put(odroidx2_dai[0].codec_of_node); ... if (mop500_dai_links[i].cpu_of_node) - of_node_put((struct device_node *) - mop500_dai_links[i].cpu_of_node); + of_node_put(mop500_dai_links[i].cpu_of_node); if (mop500_dai_links[i].codec_of_node) - of_node_put((struct device_node *) - mop500_dai_links[i].codec_of_node); + of_node_put(mop500_dai_links[i].codec_of_node); having made of_node_put() take a const pointer. Since of_node_put() ultimately modifies the data pointed to by that pointer, making its argument "const" is incorrect. Moreover, Jean's latest patch is absolutely the right thing to do. Had he quoted me fully, then the reason would become clear. 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, what you have is a pointer that you would /like/ to be const, but ultimately you violate its const-ness at some point in time when you need to call of_node_put() on it. So it isn't really const at all.
diff --git a/include/sound/soc.h b/include/sound/soc.h index 7ba7130..405f967 100644 --- a/include/sound/soc.h +++ b/include/sound/soc.h @@ -886,7 +886,7 @@ struct snd_soc_platform_driver { struct snd_soc_dai_link_component { const char *name; - const struct device_node *of_node; + struct device_node *of_node; const char *dai_name; }; @@ -990,7 +990,7 @@ struct snd_soc_codec_conf { * DT/OF node, but not both. */ const char *dev_name; - const struct device_node *of_node; + struct device_node *of_node; /* * optional map of kcontrol, widget and path name prefixes that are @@ -1007,7 +1007,7 @@ struct snd_soc_aux_dev { * DT/OF node, but not both. */ const char *codec_name; - const struct device_node *codec_of_node; + struct device_node *codec_of_node; /* codec/machine specific init - e.g. add machine controls */ int (*init)(struct snd_soc_component *component);
From Russell King: of_node_put() modifies the struct device_node contents. Therefore, of_node_put() definitely not treating the data pointed to as read-only, and therefore it is completely inappropriate for it to be marked "const". Signed-off-by: Jean-Francois Moine <moinejf@free.fr> --- include/sound/soc.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)