Messages in this thread | | | From | Sven Van Asbroeck <> | Date | Sat, 11 Jul 2020 11:08:24 -0400 | Subject | Re: sound/soc/codecs/zl38060.c:614:34: warning: unused variable 'zl38_dt_ids' |
| |
Hi Nathan and Mark,
On Fri, Jul 10, 2020 at 11:30 PM Nathan Chancellor <natechancellor@gmail.com> wrote: > > Sure, you could hide it behind an ifdef for either CONFIG_OF or MODULE > (since you could build this as a module with CONFIG_OF disabled). > > I just figured this would be something frowned upon but if that is how > you would prefer it to be fixed, then I have no objections to it. >
That's how things used to work in the past: we had to #ifdef CONFIG_OF all the driver of_XXX code, so it could be built on !CONFIG_OF.
I remember problems with this approach: it generated a lot of visual noise, it was fragile in both directions: including too much, and excluding too much. Last but not least, it required us ARM people to test build each patch on !CONFIG_OF, which many conveniently forgot to do :)
My "vote" would be to fix the warning using compiler magic. For example:
#if !CONFIG_OF // #define of_match_ptr(x) NULL #define of_match_ptr(x) ((x) == NULL ? NULL : NULL) #endif
That seems to eliminate the warning on my gcc version 7.5.0, but of course as compilers get more clever, this could eventually generate a warning (if it doesn't already on clang).
So perhaps use compiler attributes instead?
Stand-alone testable code snippet below. ======================================================
// gcc -Wall unused.c // results in: match_table is NULL // gcc -Wall -DCONFIG_OF unused.c // results in: match_table[0] = 5
#include <stdio.h>
#ifdef CONFIG_OF #define of_match_ptr(x) x #else #define of_match_ptr(x) ((x) == NULL ? NULL : NULL) #endif
struct of_device_id { int id; };
static const struct of_device_id some_ids[] = { { .id = 5, }, { /* sentinel */ } };
struct driver { const struct of_device_id *of_match_table; };
static const struct driver my_driver = { .of_match_table = of_match_ptr(some_ids), };
int main() { if (my_driver.of_match_table) printf("match_table[0] = %d\n", my_driver.of_match_table[0].id); else printf("match_table is NULL\n"); }
| |