lkml.org 
[lkml]   [2021]   [Sep]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH v2 2/3] drm/i915/utils: do not depend on config being defined
    Date
    Like the IS_ENABLED() counterpart, we can make IS_CONFIG_NONZERO() to
    return the right thing when the config is not defined rather than a
    build error, with the limitation that it can't be used on preprocessor
    context.

    The trick here is that macro names can't start with a number or dash, so
    we stringify the argument and check that the first char is a number != 0
    (or starting with a dash to cover negative numbers). Except for -O0
    builds the strings are all eliminated.

    Taking CONFIG_DRM_I915_REQUEST_TIMEOUT in
    drivers/gpu/drm/i915/gem/i915_gem_context.c as example, we have the
    following output of the preprocessor:

    old:
    if (((20000) != 0) &&
    new:
    if (( ("20000"[0] > '0' && "20000"[0] < '9') || "20000"[0] == '-' ) &&

    New one looks worse, but is also eliminated from the object:

    $ size drivers/gpu/drm/i915/gem/i915_gem_context.o.*
    text data bss dec hex filename
    52021 1070 232 53323 d04b drivers/gpu/drm/i915/gem/i915_gem_context.o.new
    52021 1070 232 53323 d04b drivers/gpu/drm/i915/gem/i915_gem_context.o.old

    Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
    ---
    drivers/gpu/drm/i915/i915_utils.h | 6 +++++-
    1 file changed, 5 insertions(+), 1 deletion(-)

    diff --git a/drivers/gpu/drm/i915/i915_utils.h b/drivers/gpu/drm/i915/i915_utils.h
    index 02bbfa4d68d3..436ce612c46a 100644
    --- a/drivers/gpu/drm/i915/i915_utils.h
    +++ b/drivers/gpu/drm/i915/i915_utils.h
    @@ -28,6 +28,7 @@
    #include <linux/list.h>
    #include <linux/overflow.h>
    #include <linux/sched.h>
    +#include <linux/stringify.h>
    #include <linux/types.h>
    #include <linux/workqueue.h>

    @@ -469,6 +470,9 @@ static inline bool timer_expired(const struct timer_list *t)
    *
    * Returns 0 if @config is 0, 1 if set to any value.
    */
    -#define IS_CONFIG_NONZERO(config) ((config) != 0)
    +#define IS_CONFIG_NONZERO(config) ( \
    + (__stringify_1(config)[0] > '0' && __stringify_1(config)[0] < '9') || \
    + __stringify_1(config)[0] == '-' \
    +)

    #endif /* !__I915_UTILS_H */
    --
    2.33.0
    \
     
     \ /
      Last update: 2021-09-29 20:34    [W:2.392 / U:0.008 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site