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From: Lucas De Marchi <lucas.demarchi@intel.com>
To: intel-gfx@lists.freedesktop.org
Cc: Daniel Vetter <daniel.vetter@intel.com>,
	dri-devel@lists.freedesktop.org,
	Masahiro Yamada <masahiroy@kernel.org>,
	linux-kernel@vger.kernel.org
Subject: [PATCH v2 2/3] drm/i915/utils: do not depend on config being defined
Date: Wed, 29 Sep 2021 11:33:56 -0700	[thread overview]
Message-ID: <20210929183357.1490204-3-lucas.demarchi@intel.com> (raw)
In-Reply-To: <20210929183357.1490204-1-lucas.demarchi@intel.com>

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


  parent reply	other threads:[~2021-09-29 18:34 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-29 18:33 [PATCH v2 0/3] Rename IS_ACTIVE() and move to kconfig.h Lucas De Marchi
2021-09-29 18:33 ` [PATCH v2 1/3] drm/i915: rename IS_ACTIVE Lucas De Marchi
2021-09-30 10:46   ` Jani Nikula
2021-09-30 15:47     ` Lucas De Marchi
2021-09-29 18:33 ` Lucas De Marchi [this message]
2021-09-29 21:08   ` [PATCH v2 2/3] drm/i915/utils: do not depend on config being defined Andrzej Hajda
2021-09-29 22:54     ` Lucas De Marchi
2021-09-30  7:01       ` Andrzej Hajda
2021-09-30 10:00   ` Steven Price
2021-09-30 15:43     ` Lucas De Marchi
2021-09-29 18:33 ` [PATCH v2 3/3] Move IS_CONFIG_NONZERO() to kconfig.h Lucas De Marchi
2021-09-30 14:01   ` Masahiro Yamada
2021-09-30 15:55     ` Lucas De Marchi
2021-10-01  2:33       ` Masahiro Yamada

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