| Message ID | 1461552642-10732-1-git-send-email-yamada.masahiro@socionext.com (mailing list archive) |
|---|---|
| State | Rejected, archived |
| Delegated to: | Stephen Boyd |
| Headers | show |
On 04/25, Masahiro Yamada wrote: > We cannot assign any value to an array type variable. So, > > hw_data->hws = kcalloc(hw_data->num, sizeof(struct clk_hw *), > GFP_KERNEL); > > fails with "invalid use of flexible array member" error. That's good. We don't want assignment to the hws member of this structure to happen from an allocation like kcalloc. > > There are two ways to fix this issue. > > [1] Make it a double-pointer > struct clk_hw_onecell_data { > size_t num; > struct clk_hw **hws; > }; > > This works as struct clk_onecell_data does. True we could go back to the old style with two allocations. > > [2] Make it a zero-sized array > struct clk_hw_onecell_data { > size_t num; > struct clk_hw *hws[0]; > }; > > This allows one-shot memory allocation like this: > > hw_data = kmalloc(sizeof(*hw_data) + clk_num * sizeof(struct clk_hw *), > GFP_KERNEL); > Good, that was possible before this patch wasn't it? > This commit adopts [2] because it looks like Stephen's intention > (he moved hws[] to the bottom of struct clk_hw_onecell_data). > > Fixes: 0861e5b8cf80 ("clk: Add clk_hw OF clk providers") > Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> > --- > > include/linux/clk-provider.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h > index fd2ccd5..1850e25 100644 > --- a/include/linux/clk-provider.h > +++ b/include/linux/clk-provider.h > @@ -769,7 +769,7 @@ struct clk_onecell_data { > > struct clk_hw_onecell_data { > size_t num; > - struct clk_hw *hws[]; > + struct clk_hw *hws[0]; I'm totally lost now. Isn't a flex array with [] or with [0] the same? The latter being a GCC extension while the former being a C99 standard?
Hi Stephen, 2016-04-26 7:27 GMT+09:00 Stephen Boyd <sboyd@codeaurora.org>: > On 04/25, Masahiro Yamada wrote: >> We cannot assign any value to an array type variable. So, >> >> hw_data->hws = kcalloc(hw_data->num, sizeof(struct clk_hw *), >> GFP_KERNEL); >> >> fails with "invalid use of flexible array member" error. > > That's good. We don't want assignment to the hws member of this > structure to happen from an allocation like kcalloc. > >> >> There are two ways to fix this issue. >> >> [1] Make it a double-pointer >> struct clk_hw_onecell_data { >> size_t num; >> struct clk_hw **hws; >> }; >> >> This works as struct clk_onecell_data does. > > True we could go back to the old style with two allocations. > >> >> [2] Make it a zero-sized array >> struct clk_hw_onecell_data { >> size_t num; >> struct clk_hw *hws[0]; >> }; >> >> This allows one-shot memory allocation like this: >> >> hw_data = kmalloc(sizeof(*hw_data) + clk_num * sizeof(struct clk_hw *), >> GFP_KERNEL); >> > > Good, that was possible before this patch wasn't it? > >> This commit adopts [2] because it looks like Stephen's intention >> (he moved hws[] to the bottom of struct clk_hw_onecell_data). >> >> Fixes: 0861e5b8cf80 ("clk: Add clk_hw OF clk providers") >> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> >> --- > >> >> include/linux/clk-provider.h | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h >> index fd2ccd5..1850e25 100644 >> --- a/include/linux/clk-provider.h >> +++ b/include/linux/clk-provider.h >> @@ -769,7 +769,7 @@ struct clk_onecell_data { >> >> struct clk_hw_onecell_data { >> size_t num; >> - struct clk_hw *hws[]; >> + struct clk_hw *hws[0]; > > I'm totally lost now. Isn't a flex array with [] or with [0] the > same? I was misunderstanding. You are right. They are the same. > The latter being a GCC extension while the former being a > C99 standard? Please ignore this patch. Sorry for noise.
diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h index fd2ccd5..1850e25 100644 --- a/include/linux/clk-provider.h +++ b/include/linux/clk-provider.h @@ -769,7 +769,7 @@ struct clk_onecell_data { struct clk_hw_onecell_data { size_t num; - struct clk_hw *hws[]; + struct clk_hw *hws[0]; }; extern struct of_device_id __clk_of_table;
We cannot assign any value to an array type variable. So, hw_data->hws = kcalloc(hw_data->num, sizeof(struct clk_hw *), GFP_KERNEL); fails with "invalid use of flexible array member" error. There are two ways to fix this issue. [1] Make it a double-pointer struct clk_hw_onecell_data { size_t num; struct clk_hw **hws; }; This works as struct clk_onecell_data does. [2] Make it a zero-sized array struct clk_hw_onecell_data { size_t num; struct clk_hw *hws[0]; }; This allows one-shot memory allocation like this: hw_data = kmalloc(sizeof(*hw_data) + clk_num * sizeof(struct clk_hw *), GFP_KERNEL); This commit adopts [2] because it looks like Stephen's intention (he moved hws[] to the bottom of struct clk_hw_onecell_data). Fixes: 0861e5b8cf80 ("clk: Add clk_hw OF clk providers") Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> --- include/linux/clk-provider.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)