[PATCH] drm/i915: Prefer struct_size over open coded arithmetic

[PATCH] drm/i915: Prefer struct_size over open coded arithmetic

[Len Baker]

As noted in the "Deprecated Interfaces, Language Features, Attributes,
and Conventions" documentation [1], size calculations (especially
multiplication) should not be performed in memory allocator (or similar)
function arguments due to the risk of them overflowing. This could lead
to values wrapping around and a smaller allocation being made than the
caller was expecting. Using those allocations could lead to linear
overflows of heap memory and other misbehaviors.

In this case these are not actually dynamic sizes: all the operands
involved in the calculation are constant values. However it is better to
refactor them anyway, just to keep the open-coded math idiom out of
code.

So, add at the end of the struct i915_syncmap a union with two flexible
array members (these arrays share the same memory layout). This is
possible using the new DECLARE_FLEX_ARRAY macro. And then, use the
struct_size() helper to do the arithmetic instead of the argument
"size + count * size" in the kmalloc and kzalloc() functions.

Also, take the opportunity to refactor the __sync_seqno and __sync_child
making them more readable.

This code was detected with the help of Coccinelle and audited and fixed
manually.

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments

Signed-off-by: Len Baker <len.baker@gmx.com>
---
 drivers/gpu/drm/i915/i915_syncmap.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_syncmap.c b/drivers/gpu/drm/i915/i915_syncmap.c
index 60404dbb2e9f..a8d35491d05a 100644
--- a/drivers/gpu/drm/i915/i915_syncmap.c
+++ b/drivers/gpu/drm/i915/i915_syncmap.c
@@ -82,6 +82,10 @@ struct i915_syncmap {
 	 *	struct i915_syncmap *child[KSYNCMAP];
 	 * };
 	 */
+	union {
+		DECLARE_FLEX_ARRAY(u32, seqno);
+		DECLARE_FLEX_ARRAY(struct i915_syncmap *, child);
+	};
 };

 /**
@@ -99,13 +103,13 @@ void i915_syncmap_init(struct i915_syncmap **root)
 static inline u32 *__sync_seqno(struct i915_syncmap *p)
 {
 	GEM_BUG_ON(p->height);
-	return (u32 *)(p + 1);
+	return p->seqno;
 }

 static inline struct i915_syncmap **__sync_child(struct i915_syncmap *p)
 {
 	GEM_BUG_ON(!p->height);
-	return (struct i915_syncmap **)(p + 1);
+	return p->child;
 }

 static inline unsigned int
@@ -200,7 +204,7 @@ __sync_alloc_leaf(struct i915_syncmap *parent, u64 id)
 {
 	struct i915_syncmap *p;

-	p = kmalloc(sizeof(*p) + KSYNCMAP * sizeof(u32), GFP_KERNEL);
+	p = kmalloc(struct_size(p, seqno, KSYNCMAP), GFP_KERNEL);
 	if (unlikely(!p))
 		return NULL;

@@ -282,7 +286,7 @@ static noinline int __sync_set(struct i915_syncmap **root, u64 id, u32 seqno)
 			unsigned int above;

 			/* Insert a join above the current layer */
-			next = kzalloc(sizeof(*next) + KSYNCMAP * sizeof(next),
+			next = kzalloc(struct_size(next, child, KSYNCMAP),
 				       GFP_KERNEL);
 			if (unlikely(!next))
 				return -ENOMEM;
--
2.25.1

Re: [PATCH] drm/i915: Prefer struct_size over open coded arithmetic

[Len Baker]

Hi,

On Sun, Oct 03, 2021 at 12:42:58PM +0200, Len Baker wrote:
> As noted in the "Deprecated Interfaces, Language Features, Attributes,
> and Conventions" documentation [1], size calculations (especially
> multiplication) should not be performed in memory allocator (or similar)
> function arguments due to the risk of them overflowing. This could lead
> to values wrapping around and a smaller allocation being made than the
> caller was expecting. Using those allocations could lead to linear
> overflows of heap memory and other misbehaviors.
>
> In this case these are not actually dynamic sizes: all the operands
> involved in the calculation are constant values. However it is better to
> refactor them anyway, just to keep the open-coded math idiom out of
> code.
>
> So, add at the end of the struct i915_syncmap a union with two flexible
> array members (these arrays share the same memory layout). This is
> possible using the new DECLARE_FLEX_ARRAY macro. And then, use the
> struct_size() helper to do the arithmetic instead of the argument
> "size + count * size" in the kmalloc and kzalloc() functions.
>
> Also, take the opportunity to refactor the __sync_seqno and __sync_child
> making them more readable.
>
> This code was detected with the help of Coccinelle and audited and fixed
> manually.
>
> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments
>
> Signed-off-by: Len Baker <len.baker@gmx.com>
> ---
>  drivers/gpu/drm/i915/i915_syncmap.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)

I received a mail telling that this patch doesn't build:

== Series Details ==

Series: drm/i915: Prefer struct_size over open coded arithmetic
URL   : https://patchwork.freedesktop.org/series/95408/
State : failure

But it builds without error against linux-next (tag next-20211001). Against
which tree and branch do I need to build?

Regards,
Len

Re: [PATCH] drm/i915: Prefer struct_size over open coded arithmetic

[Jani Nikula]

On Mon, 11 Oct 2021, Len Baker <len.baker@gmx.com> wrote:
> Hi,
>
> On Sun, Oct 03, 2021 at 12:42:58PM +0200, Len Baker wrote:
>> As noted in the "Deprecated Interfaces, Language Features, Attributes,
>> and Conventions" documentation [1], size calculations (especially
>> multiplication) should not be performed in memory allocator (or similar)
>> function arguments due to the risk of them overflowing. This could lead
>> to values wrapping around and a smaller allocation being made than the
>> caller was expecting. Using those allocations could lead to linear
>> overflows of heap memory and other misbehaviors.
>>
>> In this case these are not actually dynamic sizes: all the operands
>> involved in the calculation are constant values. However it is better to
>> refactor them anyway, just to keep the open-coded math idiom out of
>> code.
>>
>> So, add at the end of the struct i915_syncmap a union with two flexible
>> array members (these arrays share the same memory layout). This is
>> possible using the new DECLARE_FLEX_ARRAY macro. And then, use the
>> struct_size() helper to do the arithmetic instead of the argument
>> "size + count * size" in the kmalloc and kzalloc() functions.
>>
>> Also, take the opportunity to refactor the __sync_seqno and __sync_child
>> making them more readable.
>>
>> This code was detected with the help of Coccinelle and audited and fixed
>> manually.
>>
>> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments
>>
>> Signed-off-by: Len Baker <len.baker@gmx.com>
>> ---
>>  drivers/gpu/drm/i915/i915_syncmap.c | 12 ++++++++----
>>  1 file changed, 8 insertions(+), 4 deletions(-)
>
> I received a mail telling that this patch doesn't build:
>
> == Series Details ==
>
> Series: drm/i915: Prefer struct_size over open coded arithmetic
> URL   : https://patchwork.freedesktop.org/series/95408/
> State : failure
>
> But it builds without error against linux-next (tag next-20211001). Against
> which tree and branch do I need to build?

drm-tip [1]. It's a sort of linux-next for graphics. I think there are
still some branches that don't feed to linux-next.

BR,
Jani.


[1] https://cgit.freedesktop.org/drm/drm-tip


>
> Regards,
> Len

-- 
Jani Nikula, Intel Open Source Graphics Center

Re: [PATCH] drm/i915: Prefer struct_size over open coded arithmetic

[Daniel Vetter]

On Wed, Oct 13, 2021 at 02:24:05PM +0300, Jani Nikula wrote:
> On Mon, 11 Oct 2021, Len Baker <len.baker@gmx.com> wrote:
> > Hi,
> >
> > On Sun, Oct 03, 2021 at 12:42:58PM +0200, Len Baker wrote:
> >> As noted in the "Deprecated Interfaces, Language Features, Attributes,
> >> and Conventions" documentation [1], size calculations (especially
> >> multiplication) should not be performed in memory allocator (or similar)
> >> function arguments due to the risk of them overflowing. This could lead
> >> to values wrapping around and a smaller allocation being made than the
> >> caller was expecting. Using those allocations could lead to linear
> >> overflows of heap memory and other misbehaviors.
> >>
> >> In this case these are not actually dynamic sizes: all the operands
> >> involved in the calculation are constant values. However it is better to
> >> refactor them anyway, just to keep the open-coded math idiom out of
> >> code.
> >>
> >> So, add at the end of the struct i915_syncmap a union with two flexible
> >> array members (these arrays share the same memory layout). This is
> >> possible using the new DECLARE_FLEX_ARRAY macro. And then, use the
> >> struct_size() helper to do the arithmetic instead of the argument
> >> "size + count * size" in the kmalloc and kzalloc() functions.
> >>
> >> Also, take the opportunity to refactor the __sync_seqno and __sync_child
> >> making them more readable.
> >>
> >> This code was detected with the help of Coccinelle and audited and fixed
> >> manually.
> >>
> >> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments
> >>
> >> Signed-off-by: Len Baker <len.baker@gmx.com>
> >> ---
> >>  drivers/gpu/drm/i915/i915_syncmap.c | 12 ++++++++----
> >>  1 file changed, 8 insertions(+), 4 deletions(-)
> >
> > I received a mail telling that this patch doesn't build:
> >
> > == Series Details ==
> >
> > Series: drm/i915: Prefer struct_size over open coded arithmetic
> > URL   : https://patchwork.freedesktop.org/series/95408/
> > State : failure
> >
> > But it builds without error against linux-next (tag next-20211001). Against
> > which tree and branch do I need to build?
> 
> drm-tip [1]. It's a sort of linux-next for graphics. I think there are
> still some branches that don't feed to linux-next.

Yeah we need to get gt-next in linux-next asap. Joonas promised to send
out his patch to make that happen in dim.
-Daniel

> 
> BR,
> Jani.
> 
> 
> [1] https://cgit.freedesktop.org/drm/drm-tip
> 
> 
> >
> > Regards,
> > Len
> 
> -- 
> Jani Nikula, Intel Open Source Graphics Center

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

Re: [PATCH] drm/i915: Prefer struct_size over open coded arithmetic

[Len Baker]

Hi Daniel and Jani,

On Wed, Oct 13, 2021 at 01:51:30PM +0200, Daniel Vetter wrote:
> On Wed, Oct 13, 2021 at 02:24:05PM +0300, Jani Nikula wrote:
> > On Mon, 11 Oct 2021, Len Baker <len.baker@gmx.com> wrote:
> > > Hi,
> > >
> > > On Sun, Oct 03, 2021 at 12:42:58PM +0200, Len Baker wrote:
> > >> As noted in the "Deprecated Interfaces, Language Features, Attributes,
> > >> and Conventions" documentation [1], size calculations (especially
> > >> multiplication) should not be performed in memory allocator (or similar)
> > >> function arguments due to the risk of them overflowing. This could lead
> > >> to values wrapping around and a smaller allocation being made than the
> > >> caller was expecting. Using those allocations could lead to linear
> > >> overflows of heap memory and other misbehaviors.
> > >>
> > >> In this case these are not actually dynamic sizes: all the operands
> > >> involved in the calculation are constant values. However it is better to
> > >> refactor them anyway, just to keep the open-coded math idiom out of
> > >> code.
> > >>
> > >> So, add at the end of the struct i915_syncmap a union with two flexible
> > >> array members (these arrays share the same memory layout). This is
> > >> possible using the new DECLARE_FLEX_ARRAY macro. And then, use the
> > >> struct_size() helper to do the arithmetic instead of the argument
> > >> "size + count * size" in the kmalloc and kzalloc() functions.
> > >>
> > >> Also, take the opportunity to refactor the __sync_seqno and __sync_child
> > >> making them more readable.
> > >>
> > >> This code was detected with the help of Coccinelle and audited and fixed
> > >> manually.
> > >>
> > >> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments
> > >>
> > >> Signed-off-by: Len Baker <len.baker@gmx.com>
> > >> ---
> > >>  drivers/gpu/drm/i915/i915_syncmap.c | 12 ++++++++----
> > >>  1 file changed, 8 insertions(+), 4 deletions(-)
> > >
> > > I received a mail telling that this patch doesn't build:
> > >
> > > == Series Details ==
> > >
> > > Series: drm/i915: Prefer struct_size over open coded arithmetic
> > > URL   : https://patchwork.freedesktop.org/series/95408/
> > > State : failure
> > >
> > > But it builds without error against linux-next (tag next-20211001). Against
> > > which tree and branch do I need to build?
> >
> > drm-tip [1]. It's a sort of linux-next for graphics. I think there are
> > still some branches that don't feed to linux-next.
>
> Yeah we need to get gt-next in linux-next asap. Joonas promised to send
> out his patch to make that happen in dim.
> -Daniel

Is there a possibility that you give an "Acked-by" tag? And then this patch
goes to the mainline through the Kees' tree or Gustavo's tree?

Or is it better to wait for drm-tip to update?

Regards,
Len

>
> >
> > BR,
> > Jani.
> >
> >
> > [1] https://cgit.freedesktop.org/drm/drm-tip
> >
> >
> > >
> > > Regards,
> > > Len
> >
> > --
> > Jani Nikula, Intel Open Source Graphics Center
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch

Re: [PATCH] drm/i915: Prefer struct_size over open coded arithmetic

[Jani Nikula]

On Sat, 16 Oct 2021, Len Baker <len.baker@gmx.com> wrote:
> Hi Daniel and Jani,
>
> On Wed, Oct 13, 2021 at 01:51:30PM +0200, Daniel Vetter wrote:
>> On Wed, Oct 13, 2021 at 02:24:05PM +0300, Jani Nikula wrote:
>> > On Mon, 11 Oct 2021, Len Baker <len.baker@gmx.com> wrote:
>> > > Hi,
>> > >
>> > > On Sun, Oct 03, 2021 at 12:42:58PM +0200, Len Baker wrote:
>> > >> As noted in the "Deprecated Interfaces, Language Features, Attributes,
>> > >> and Conventions" documentation [1], size calculations (especially
>> > >> multiplication) should not be performed in memory allocator (or similar)
>> > >> function arguments due to the risk of them overflowing. This could lead
>> > >> to values wrapping around and a smaller allocation being made than the
>> > >> caller was expecting. Using those allocations could lead to linear
>> > >> overflows of heap memory and other misbehaviors.
>> > >>
>> > >> In this case these are not actually dynamic sizes: all the operands
>> > >> involved in the calculation are constant values. However it is better to
>> > >> refactor them anyway, just to keep the open-coded math idiom out of
>> > >> code.
>> > >>
>> > >> So, add at the end of the struct i915_syncmap a union with two flexible
>> > >> array members (these arrays share the same memory layout). This is
>> > >> possible using the new DECLARE_FLEX_ARRAY macro. And then, use the
>> > >> struct_size() helper to do the arithmetic instead of the argument
>> > >> "size + count * size" in the kmalloc and kzalloc() functions.
>> > >>
>> > >> Also, take the opportunity to refactor the __sync_seqno and __sync_child
>> > >> making them more readable.
>> > >>
>> > >> This code was detected with the help of Coccinelle and audited and fixed
>> > >> manually.
>> > >>
>> > >> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments
>> > >>
>> > >> Signed-off-by: Len Baker <len.baker@gmx.com>
>> > >> ---
>> > >>  drivers/gpu/drm/i915/i915_syncmap.c | 12 ++++++++----
>> > >>  1 file changed, 8 insertions(+), 4 deletions(-)
>> > >
>> > > I received a mail telling that this patch doesn't build:
>> > >
>> > > == Series Details ==
>> > >
>> > > Series: drm/i915: Prefer struct_size over open coded arithmetic
>> > > URL   : https://patchwork.freedesktop.org/series/95408/
>> > > State : failure
>> > >
>> > > But it builds without error against linux-next (tag next-20211001). Against
>> > > which tree and branch do I need to build?
>> >
>> > drm-tip [1]. It's a sort of linux-next for graphics. I think there are
>> > still some branches that don't feed to linux-next.
>>
>> Yeah we need to get gt-next in linux-next asap. Joonas promised to send
>> out his patch to make that happen in dim.
>> -Daniel
>
> Is there a possibility that you give an "Acked-by" tag? And then this patch
> goes to the mainline through the Kees' tree or Gustavo's tree?

If this does not apply to drm-intel-gt-next (or drm-tip), applying it to
some other branch will just cause unnecessary conflicts later on. It's
unnecessary extra work. It's not an urgent fix or anything, there is no
reason to do that. So that's a NAK.

> Or is it better to wait for drm-tip to update?

drm-tip is up to date, it's just that one of the branches that feed to
it is (was?) not feeding to linux-next.

If you're contributing to drm, please consider basing your patches on
top of drm-tip.


BR,
Jani.


>
> Regards,
> Len
>
>>
>> >
>> > BR,
>> > Jani.
>> >
>> >
>> > [1] https://cgit.freedesktop.org/drm/drm-tip
>> >
>> >
>> > >
>> > > Regards,
>> > > Len
>> >
>> > --
>> > Jani Nikula, Intel Open Source Graphics Center
>>
>> --
>> Daniel Vetter
>> Software Engineer, Intel Corporation
>> http://blog.ffwll.ch

-- 
Jani Nikula, Intel Open Source Graphics Center

Re: [PATCH] drm/i915: Prefer struct_size over open coded arithmetic

[Len Baker]

Hi Jani,

On Mon, Oct 18, 2021 at 01:00:01PM +0300, Jani Nikula wrote:
> On Sat, 16 Oct 2021, Len Baker <len.baker@gmx.com> wrote:
> > Hi Daniel and Jani,
> >
> > On Wed, Oct 13, 2021 at 01:51:30PM +0200, Daniel Vetter wrote:
> >> On Wed, Oct 13, 2021 at 02:24:05PM +0300, Jani Nikula wrote:
> >> > On Mon, 11 Oct 2021, Len Baker <len.baker@gmx.com> wrote:
> >> > > Hi,
> >> > >
> >> > > On Sun, Oct 03, 2021 at 12:42:58PM +0200, Len Baker wrote:
> >> > >> As noted in the "Deprecated Interfaces, Language Features, Attributes,
> >> > >> and Conventions" documentation [1], size calculations (especially
> >> > >> multiplication) should not be performed in memory allocator (or similar)
> >> > >> function arguments due to the risk of them overflowing. This could lead
> >> > >> to values wrapping around and a smaller allocation being made than the
> >> > >> caller was expecting. Using those allocations could lead to linear
> >> > >> overflows of heap memory and other misbehaviors.
> >> > >>
> >> > >> In this case these are not actually dynamic sizes: all the operands
> >> > >> involved in the calculation are constant values. However it is better to
> >> > >> refactor them anyway, just to keep the open-coded math idiom out of
> >> > >> code.
> >> > >>
> >> > >> So, add at the end of the struct i915_syncmap a union with two flexible
> >> > >> array members (these arrays share the same memory layout). This is
> >> > >> possible using the new DECLARE_FLEX_ARRAY macro. And then, use the
> >> > >> struct_size() helper to do the arithmetic instead of the argument
> >> > >> "size + count * size" in the kmalloc and kzalloc() functions.
> >> > >>
> >> > >> Also, take the opportunity to refactor the __sync_seqno and __sync_child
> >> > >> making them more readable.
> >> > >>
> >> > >> This code was detected with the help of Coccinelle and audited and fixed
> >> > >> manually.
> >> > >>
> >> > >> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments
> >> > >>
> >> > >> Signed-off-by: Len Baker <len.baker@gmx.com>
> >> > >> ---
> >> > >>  drivers/gpu/drm/i915/i915_syncmap.c | 12 ++++++++----
> >> > >>  1 file changed, 8 insertions(+), 4 deletions(-)
> >> > >
> >> > > I received a mail telling that this patch doesn't build:
> >> > >
> >> > > == Series Details ==
> >> > >
> >> > > Series: drm/i915: Prefer struct_size over open coded arithmetic
> >> > > URL   : https://patchwork.freedesktop.org/series/95408/
> >> > > State : failure
> >> > >
> >> > > But it builds without error against linux-next (tag next-20211001). Against
> >> > > which tree and branch do I need to build?
> >> >
> >> > drm-tip [1]. It's a sort of linux-next for graphics. I think there are
> >> > still some branches that don't feed to linux-next.
> >>
> >> Yeah we need to get gt-next in linux-next asap. Joonas promised to send
> >> out his patch to make that happen in dim.
> >> -Daniel
> >
> > Is there a possibility that you give an "Acked-by" tag? And then this patch
> > goes to the mainline through the Kees' tree or Gustavo's tree?
>
> If this does not apply to drm-intel-gt-next (or drm-tip), applying it to
> some other branch will just cause unnecessary conflicts later on. It's
> unnecessary extra work. It's not an urgent fix or anything, there is no
> reason to do that. So that's a NAK.

Ok. Understood.

> > Or is it better to wait for drm-tip to update?
>
> drm-tip is up to date, it's just that one of the branches that feed to
> it is (was?) not feeding to linux-next.

Sorry, but I'm missing something here. In linux-next this is the commit
history of include/linux/stddef.h file:

3080ea5553cc stddef: Introduce DECLARE_FLEX_ARRAY() helper
50d7bd38c3aa stddef: Introduce struct_group() helper macro
e7f18c22e6be stddef: Fix kerndoc for sizeof_field() and offsetofend()
4229a470175b stddef.h: Introduce sizeof_field()
...

But in drm-tip this is the commit history:

4229a470175b stddef.h: Introduce sizeof_field()
...

For this patch the DECLARE_FLEX_ARRAY() helper is needed. But the build
fails due to the last tree commits for stddef.h file are not present.
So, if I understand correctly, drm-tip is not up to date with linux-next.

Regards,
Len

>
> If you're contributing to drm, please consider basing your patches on
> top of drm-tip.
>
>
> BR,
> Jani.
>
>
> >
> > Regards,
> > Len
> >
> >>
> >> >
> >> > BR,
> >> > Jani.
> >> >
> >> >
> >> > [1] https://cgit.freedesktop.org/drm/drm-tip
> >> >
> >> >
> >> > >
> >> > > Regards,
> >> > > Len
> >> >
> >> > --
> >> > Jani Nikula, Intel Open Source Graphics Center
> >>
> >> --
> >> Daniel Vetter
> >> Software Engineer, Intel Corporation
> >> http://blog.ffwll.ch
>
> --
> Jani Nikula, Intel Open Source Graphics Center

Re: [PATCH] drm/i915: Prefer struct_size over open coded arithmetic

[Jani Nikula]

On Sat, 23 Oct 2021, Len Baker <len.baker@gmx.com> wrote:
> Sorry, but I'm missing something here. In linux-next this is the commit
> history of include/linux/stddef.h file:
>
> 3080ea5553cc stddef: Introduce DECLARE_FLEX_ARRAY() helper
> 50d7bd38c3aa stddef: Introduce struct_group() helper macro
> e7f18c22e6be stddef: Fix kerndoc for sizeof_field() and offsetofend()
> 4229a470175b stddef.h: Introduce sizeof_field()
> ...
>
> But in drm-tip this is the commit history:
>
> 4229a470175b stddef.h: Introduce sizeof_field()
> ...
>
> For this patch the DECLARE_FLEX_ARRAY() helper is needed. But the build
> fails due to the last tree commits for stddef.h file are not present.
> So, if I understand correctly, drm-tip is not up to date with linux-next.

linux-next is an ephemeral integration branch for most arch, subsystem
and driver -next branches.

drm-tip is an ephemeral integration branch for drm subsystem and driver
-next branches.

They contain different sets of branches. They are constantly
rebuilt. They are not the end result or end goal.

If a problem (or a solution, for that matter) only exists in the merge
of some of those branches, you can't actually fix it until such a merge
exists somewhere more permanent than an ephemeral integration branch.


BR,
Jani.


-- 
Jani Nikula, Intel Open Source Graphics Center

Re: [PATCH] drm/i915: Prefer struct_size over open coded arithmetic

[Len Baker]

Hi,

On Wed, Oct 27, 2021 at 06:06:28PM +0300, Jani Nikula wrote:
> On Sat, 23 Oct 2021, Len Baker <len.baker@gmx.com> wrote:
> > Sorry, but I'm missing something here. In linux-next this is the commit
> > history of include/linux/stddef.h file:
> >
> > 3080ea5553cc stddef: Introduce DECLARE_FLEX_ARRAY() helper
> > 50d7bd38c3aa stddef: Introduce struct_group() helper macro
> > e7f18c22e6be stddef: Fix kerndoc for sizeof_field() and offsetofend()
> > 4229a470175b stddef.h: Introduce sizeof_field()
> > ...
> >
> > But in drm-tip this is the commit history:
> >
> > 4229a470175b stddef.h: Introduce sizeof_field()
> > ...
> >
> > For this patch the DECLARE_FLEX_ARRAY() helper is needed. But the build
> > fails due to the last tree commits for stddef.h file are not present.
> > So, if I understand correctly, drm-tip is not up to date with linux-next.
>
> linux-next is an ephemeral integration branch for most arch, subsystem
> and driver -next branches.
>
> drm-tip is an ephemeral integration branch for drm subsystem and driver
> -next branches.
>
> They contain different sets of branches. They are constantly
> rebuilt. They are not the end result or end goal.
>
> If a problem (or a solution, for that matter) only exists in the merge
> of some of those branches, you can't actually fix it until such a merge
> exists somewhere more permanent than an ephemeral integration branch.

Ok, understood. Thanks for the clarification.

Regards,
Len