arch/powerpc/platforms/powermac/backlight.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-)
From: Markus Elfring <elfring@users.sourceforge.net>
Date: Wed, 2 Oct 2024 21:50:27 +0200
An of_node_put(bk_node) call was immediately used after a pointer check
for an of_get_property() call in this function implementation.
Thus call such a function only once instead directly before the check.
This issue was transformed by using the Coccinelle software.
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
---
arch/powerpc/platforms/powermac/backlight.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/arch/powerpc/platforms/powermac/backlight.c b/arch/powerpc/platforms/powermac/backlight.c
index 12bc01353bd3..d3666595a62e 100644
--- a/arch/powerpc/platforms/powermac/backlight.c
+++ b/arch/powerpc/platforms/powermac/backlight.c
@@ -61,11 +61,9 @@ int pmac_has_backlight_type(const char *type)
if (bk_node) {
const char *prop = of_get_property(bk_node,
"backlight-control", NULL);
- if (prop && strncmp(prop, type, strlen(type)) == 0) {
- of_node_put(bk_node);
- return 1;
- }
of_node_put(bk_node);
+ if (prop && strncmp(prop, type, strlen(type)) == 0)
+ return 1;
}
return 0;
--
2.46.1
Le 02/10/2024 à 22:02, Markus Elfring a écrit :
> From: Markus Elfring <elfring@users.sourceforge.net>
> Date: Wed, 2 Oct 2024 21:50:27 +0200
>
> An of_node_put(bk_node) call was immediately used after a pointer check
> for an of_get_property() call in this function implementation.
> Thus call such a function only once instead directly before the check.
It seems pointless to perform a put immediately after a get. Shouldn't
of_find_property() be used instead ? And then of_property_read_string()
would probably be better.
Maybe you can even use of_property_match_string().
>
> This issue was transformed by using the Coccinelle software.
>
> Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
> ---
> arch/powerpc/platforms/powermac/backlight.c | 6 ++----
> 1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/arch/powerpc/platforms/powermac/backlight.c b/arch/powerpc/platforms/powermac/backlight.c
> index 12bc01353bd3..d3666595a62e 100644
> --- a/arch/powerpc/platforms/powermac/backlight.c
> +++ b/arch/powerpc/platforms/powermac/backlight.c
> @@ -61,11 +61,9 @@ int pmac_has_backlight_type(const char *type)
> if (bk_node) {
> const char *prop = of_get_property(bk_node,
> "backlight-control", NULL);
> - if (prop && strncmp(prop, type, strlen(type)) == 0) {
> - of_node_put(bk_node);
> - return 1;
> - }
> of_node_put(bk_node);
> + if (prop && strncmp(prop, type, strlen(type)) == 0)
> + return 1;
> }
>
> return 0;
> --
> 2.46.1
>
Christophe Leroy <christophe.leroy@csgroup.eu> writes:
> Le 02/10/2024 à 22:02, Markus Elfring a écrit :
>> From: Markus Elfring <elfring@users.sourceforge.net>
>> Date: Wed, 2 Oct 2024 21:50:27 +0200
>>
>> An of_node_put(bk_node) call was immediately used after a pointer check
>> for an of_get_property() call in this function implementation.
>> Thus call such a function only once instead directly before the check.
>
> It seems pointless to perform a put immediately after a get. Shouldn't
> of_find_property() be used instead ? And then of_property_read_string()
> would probably be better.
>
> Maybe you can even use of_property_match_string().
Yes that would clean it up nicely I think, eg:
int pmac_has_backlight_type(const char *type)
{
struct device_node* bk_node = of_find_node_by_name(NULL, "backlight");
int i;
i = of_property_match_string(bk_node, "backlight-control", type);
of_node_put(bk_node);
return i >= 0;
}
cheers
First of all, the change is wrong. We can't dereference "prop" after calling of_node_put(). You have to be a bit extra careful reviewing Markus's patches because a lot of the rest of us have blocked these messages so you're on your own in that way. On Wed, Oct 02, 2024 at 10:43:46PM +0200, Christophe Leroy wrote: > > > Le 02/10/2024 à 22:02, Markus Elfring a écrit : > > From: Markus Elfring <elfring@users.sourceforge.net> > > Date: Wed, 2 Oct 2024 21:50:27 +0200 > > > > An of_node_put(bk_node) call was immediately used after a pointer check > > for an of_get_property() call in this function implementation. > > Thus call such a function only once instead directly before the check. > > It seems pointless to perform a put immediately after a get. Shouldn't > of_find_property() be used instead ? And then of_property_read_string() > would probably be better. > > Maybe you can even use of_property_match_string(). The of_get_property() function doesn't do a get as in get/put, it just finds the property and returns it. It doesn't bump the reference count. It's a confusing name in that way. The The of_node_put() pairs with of_find_node_by_name(). regards, dan carpenter
> First of all, the change is wrong. We can't dereference "prop" after calling > of_node_put(). … > The of_get_property() function doesn't do a get as in get/put, it just finds > the property and returns it. It doesn't bump the reference count. It's a > confusing name in that way. The The of_node_put() pairs with > of_find_node_by_name(). Thanks for your information. * Do you see opportunities for improving the software documentation accordingly? * How much can source code analysis tools influence development efforts? Regards, Markus
On 03/10/2024 07:56, Dan Carpenter wrote: > First of all, the change is wrong. We can't dereference "prop" after calling > of_node_put(). You have to be a bit extra careful reviewing Markus's patches > because a lot of the rest of us have blocked these messages so you're on your > own in that way. Yep, I plonked him some time ago and everything is in spam. The code looks just incorrect and I think Markus did not understand it before transforming. Best regards, Krzysztof
From: Markus Elfring <elfring@users.sourceforge.net>
Date: Fri, 11 Oct 2024 18:10:06 +0200
Replace an of_get_property() call by of_property_match_string()
so that this function implementation can be simplified.
Suggested-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Link: https://lore.kernel.org/linuxppc-dev/d9bdc1b6-ea7e-47aa-80aa-02ae649abf72@csgroup.eu/
Suggested-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/linuxppc-dev/87cyk97ufp.fsf@mail.lhotse/
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
---
arch/powerpc/platforms/powermac/backlight.c | 14 +++-----------
1 file changed, 3 insertions(+), 11 deletions(-)
diff --git a/arch/powerpc/platforms/powermac/backlight.c b/arch/powerpc/platforms/powermac/backlight.c
index 12bc01353bd3..79741370c40c 100644
--- a/arch/powerpc/platforms/powermac/backlight.c
+++ b/arch/powerpc/platforms/powermac/backlight.c
@@ -57,18 +57,10 @@ struct backlight_device *pmac_backlight;
int pmac_has_backlight_type(const char *type)
{
struct device_node* bk_node = of_find_node_by_name(NULL, "backlight");
+ int i = of_property_match_string(bk_node, "backlight-control", type);
- if (bk_node) {
- const char *prop = of_get_property(bk_node,
- "backlight-control", NULL);
- if (prop && strncmp(prop, type, strlen(type)) == 0) {
- of_node_put(bk_node);
- return 1;
- }
- of_node_put(bk_node);
- }
-
- return 0;
+ of_node_put(bk_node);
+ return i >= 0;
}
static void pmac_backlight_key_worker(struct work_struct *work)
--
2.46.1On Fri, 11 Oct 2024 18:18:42 +0200, Markus Elfring wrote:
> Replace an of_get_property() call by of_property_match_string()
> so that this function implementation can be simplified.
>
>
Applied to powerpc/next.
[1/1] powermac: Use of_property_match_string() in pmac_has_backlight_type()
https://git.kernel.org/powerpc/c/2e716f5cdebed2fb98cafffaf626645c2e922dbb
cheers
Le 11/10/2024 à 18:18, Markus Elfring a écrit :
> From: Markus Elfring <elfring@users.sourceforge.net>
> Date: Fri, 11 Oct 2024 18:10:06 +0200
>
> Replace an of_get_property() call by of_property_match_string()
> so that this function implementation can be simplified.
>
> Suggested-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> Link: https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kernel.org%2Flinuxppc-dev%2Fd9bdc1b6-ea7e-47aa-80aa-02ae649abf72%40csgroup.eu%2F&data=05%7C02%7Cchristophe.leroy%40csgroup.eu%7Cf278e44683c04b931b9c08dcea106447%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C638642603333398766%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=6byvgvuGiBSVu8F6kLA2OozUuHZunJRH%2BU%2Bq9q7osmM%3D&reserved=0
> Suggested-by: Michael Ellerman <mpe@ellerman.id.au>
> Link: https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kernel.org%2Flinuxppc-dev%2F87cyk97ufp.fsf%40mail.lhotse%2F&data=05%7C02%7Cchristophe.leroy%40csgroup.eu%7Cf278e44683c04b931b9c08dcea106447%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C638642603333422636%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=IDuYfe3UoaIEmedJ07H67zvzrPnzbQ2g8EeTtbJ%2BbZ8%3D&reserved=0
> Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
> ---
> arch/powerpc/platforms/powermac/backlight.c | 14 +++-----------
> 1 file changed, 3 insertions(+), 11 deletions(-)
>
> diff --git a/arch/powerpc/platforms/powermac/backlight.c b/arch/powerpc/platforms/powermac/backlight.c
> index 12bc01353bd3..79741370c40c 100644
> --- a/arch/powerpc/platforms/powermac/backlight.c
> +++ b/arch/powerpc/platforms/powermac/backlight.c
> @@ -57,18 +57,10 @@ struct backlight_device *pmac_backlight;
> int pmac_has_backlight_type(const char *type)
> {
> struct device_node* bk_node = of_find_node_by_name(NULL, "backlight");
> + int i = of_property_match_string(bk_node, "backlight-control", type);
>
> - if (bk_node) {
> - const char *prop = of_get_property(bk_node,
> - "backlight-control", NULL);
> - if (prop && strncmp(prop, type, strlen(type)) == 0) {
> - of_node_put(bk_node);
> - return 1;
> - }
> - of_node_put(bk_node);
> - }
> -
> - return 0;
> + of_node_put(bk_node);
> + return i >= 0;
Could have been:
return !IS_ERR_VALUE(i);
Never mind,
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> }
>
> static void pmac_backlight_key_worker(struct work_struct *work)
> --
> 2.46.1
>
On Fri, Oct 11, 2024 at 06:25:45PM +0200, Christophe Leroy wrote:
> > diff --git a/arch/powerpc/platforms/powermac/backlight.c b/arch/powerpc/platforms/powermac/backlight.c
> > index 12bc01353bd3..79741370c40c 100644
> > --- a/arch/powerpc/platforms/powermac/backlight.c
> > +++ b/arch/powerpc/platforms/powermac/backlight.c
> > @@ -57,18 +57,10 @@ struct backlight_device *pmac_backlight;
> > int pmac_has_backlight_type(const char *type)
> > {
> > struct device_node* bk_node = of_find_node_by_name(NULL, "backlight");
> > + int i = of_property_match_string(bk_node, "backlight-control", type);
> >
> > - if (bk_node) {
> > - const char *prop = of_get_property(bk_node,
> > - "backlight-control", NULL);
> > - if (prop && strncmp(prop, type, strlen(type)) == 0) {
> > - of_node_put(bk_node);
> > - return 1;
> > - }
> > - of_node_put(bk_node);
> > - }
> > -
> > - return 0;
> > + of_node_put(bk_node);
> > + return i >= 0;
>
> Could have been:
>
> return !IS_ERR_VALUE(i);
>
IS_ERR_VALUE() macro should only be used when you're dealing with memory
addresses. What I mean is there places in mm/ where we pass addresses as
unsigned long values instead of pointers. For example, get_unmapped_area()
returns unsigned long. The IS_ERR_VALUE() macro is necessary for that.
For regular error codes, we can just check for negatives. we don't have do
anything fancy.
Of course, you can find counter examples, like msm_iommu_attach_dev() or
st_fdma_of_xlate(). <small joke>But in those cases, it's done to deliberately
to ensure that the code will never accidentally get built on 64bit systems.
</small joke>
regards,
dan carpenter
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