Messages in this thread Patch in this message | | | From | Alejandro Colomar <> | Subject | [PATCH] linux/container_of.h: Add memberof() | Date | Sun, 20 Aug 2023 21:52:22 +0200 |
| |
From: Alejandro Colomar <alx.manpages@gmail.com>
Hi!
On 2023-08-18 10:46, Andy Shevchenko wrote: > On Fri, Aug 18, 2023 at 01:28:42PM +0800, Herbert Xu wrote: >> On Thu, Aug 17, 2023 at 04:33:17PM +0200, Lucas Segarra Fernandez wrote: >>> >>> +static struct pm_status_row pm_event_rows[] = { >>> + PM_INFO_REGSET_ENTRY32(event_log[0], EVENT0), >>> + PM_INFO_REGSET_ENTRY32(event_log[1], EVENT1), >>> + PM_INFO_REGSET_ENTRY32(event_log[2], EVENT2), >>> + PM_INFO_REGSET_ENTRY32(event_log[3], EVENT3), >>> + PM_INFO_REGSET_ENTRY32(event_log[4], EVENT4), >>> + PM_INFO_REGSET_ENTRY32(event_log[5], EVENT5), >>> + PM_INFO_REGSET_ENTRY32(event_log[6], EVENT6), >>> + PM_INFO_REGSET_ENTRY32(event_log[7], EVENT7), >>> +}; >>> + >>> +static_assert(ARRAY_SIZE_OF_FIELD(struct icp_qat_fw_init_admin_pm_info, event_log) == >>> + ARRAY_SIZE(pm_event_rows));
How about the following?
static_assert(ARRAY_SIZE(pm_event_rows) == ARRAY_SIZE(memberof(struct icp_qat_fw_init_admin_pm_info, event_log)));
It would only need one macro addition, without significant churn. It's even less typing. Below is a scissor patch with the addition of memberof().
I tried building the kernel, and didn't see any warnings form the patch below.
Cheers, Alex
>> >> Was all of that churn just for this one line? >> >> How about simply declaring a macro >> >> #define QAT_NUMBER_OF_PM_EVENTS 8 >> >> and then use it for the two arrays: >> >> static struct pm_status_row pm_event_rows[QAT_NUMBER_OF_PM_EVENTS] = { >> >> __u32 event_log[QAT_NUMBER_OF_PM_EVENTS]; >> >> What am I missing? > > Splitting ARRAY_SIZE() is very beneficial on its own. > The static assert is slightly more robust for the big code then defining > something that at some point can be missed or miscalculated. Yet we can > survive with a macro if you thinks it's better. >
-----8<------------
Many xxxof_{member,field}() macros make use of the same construction to refer to a member of a struct without needing a variable of the structure type.
memberof(T, m) simplifies all of those, avoids possible mistakes in repetition, adds a meaningful name to the construction, and improves readability by avoiding too many parentheses together.
It uses a compound literal, which should optimized out by the compiler. It's a bit simpler to read than the dereference of a casted null pointer, due to having less parentheses in the implementation.
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Cc: Herbert Xu <herbert@gondor.apana.org.au> Cc: Lucas Segarra Fernandez <lucas.segarra.fernandez@intel.com> Cc: Giovanni Cabiddu <giovanni.cabiddu@intel.com> Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com> --- include/linux/container_of.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/include/linux/container_of.h b/include/linux/container_of.h index 713890c867be..5e762025c780 100644 --- a/include/linux/container_of.h +++ b/include/linux/container_of.h @@ -5,7 +5,9 @@ #include <linux/build_bug.h> #include <linux/stddef.h> -#define typeof_member(T, m) typeof(((T*)0)->m) + +#define memberof(T, member) ((T){}.member) +#define typeof_member(T, m) typeof(memberof(T, m)) /** * container_of - cast a member of a structure out to the containing structure -- 2.40.1
| |