linux-kernel - [PATCH v2 3/9] drm/print: Fix support for NULL as first argument of drm_dbg

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Message-ID: <cd397a877b94ec8062440e3ae6a6a4f1af82d854.1671723195.git.code@siddh.me>
Date:   Thu, 22 Dec 2022 21:10:37 +0530
From:   Siddh Raman Pant <code@...dh.me>
To:     Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Simon Ser <contact@...rsion.fr>
Cc:     dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: [PATCH v2 3/9] drm/print: Fix support for NULL as first argument of drm_dbg_*

Comments say macros DRM_DEBUG_* are deprecated in favor of
drm_dbg_*(NULL, ...), but they have broken support for it,
as the macro will result in `(NULL) ? (NULL)->dev : NULL`.

Thus, fix them by separating logic to get dev ptr in a new
function, which will return the dev ptr if arg is not NULL.
Use it in drm_dbg_*, and also in __DRM_DEFINE_DBG_RATELIMITED,
where a similar (but correct) NULL check was in place.

Signed-off-by: Siddh Raman Pant <code@...dh.me>
---
 include/drm/drm_print.h | 42 ++++++++++++++++++++++++++++-------------
 1 file changed, 29 insertions(+), 13 deletions(-)

diff --git a/include/drm/drm_print.h b/include/drm/drm_print.h
index a44fb7ef257f..6d2d5c522e25 100644
--- a/include/drm/drm_print.h
+++ b/include/drm/drm_print.h
@@ -34,6 +34,7 @@
 #include <linux/dynamic_debug.h>
 
 #include <drm/drm.h>
+#include <drm/drm_device.h>
 
 /* Do *not* use outside of drm_print.[ch]! */
 extern unsigned long __drm_debug;
@@ -451,6 +452,22 @@ void __drm_dev_dbg(struct _ddebug *desc, const struct device *dev,
  * Prefer drm_device based logging over device or prink based logging.
  */
 
+/**
+ * __drm_get_dev_ptr - Helper function to get device type pointer even if NULL
+ *		       is passed. Primarily for use in print macros, since they
+ *		       need to handle NULL as the first argument passed.
+ * @drm: The *drm_device pointer, or NULL.
+ *
+ * RETURNS:
+ * The *device pointer, or NULL.
+ */
+static inline struct device *__drm_get_dev_ptr(const struct drm_device *drm)
+{
+	if (drm)
+		return drm->dev;
+	return NULL;
+}
+
 /* Helper for struct drm_device based logging. */
 #define __drm_printk(drm, level, type, fmt, ...)			\
 	dev_##level##type((drm)->dev, "[drm] " fmt, ##__VA_ARGS__)
@@ -487,25 +504,25 @@ void __drm_dev_dbg(struct _ddebug *desc, const struct device *dev,
 
 
 #define drm_dbg_core(drm, fmt, ...)					\
-	drm_dev_dbg((drm) ? (drm)->dev : NULL, DRM_UT_CORE, fmt, ##__VA_ARGS__)
-#define drm_dbg_driver(drm, fmt, ...)						\
-	drm_dev_dbg((drm) ? (drm)->dev : NULL, DRM_UT_DRIVER, fmt, ##__VA_ARGS__)
+	drm_dev_dbg(__drm_get_dev_ptr(drm), DRM_UT_CORE, fmt, ##__VA_ARGS__)
+#define drm_dbg_driver(drm, fmt, ...)					\
+	drm_dev_dbg(__drm_get_dev_ptr(drm), DRM_UT_DRIVER, fmt, ##__VA_ARGS__)
 #define drm_dbg_kms(drm, fmt, ...)					\
-	drm_dev_dbg((drm) ? (drm)->dev : NULL, DRM_UT_KMS, fmt, ##__VA_ARGS__)
+	drm_dev_dbg(__drm_get_dev_ptr(drm), DRM_UT_KMS, fmt, ##__VA_ARGS__)
 #define drm_dbg_prime(drm, fmt, ...)					\
-	drm_dev_dbg((drm) ? (drm)->dev : NULL, DRM_UT_PRIME, fmt, ##__VA_ARGS__)
+	drm_dev_dbg(__drm_get_dev_ptr(drm), DRM_UT_PRIME, fmt, ##__VA_ARGS__)
 #define drm_dbg_atomic(drm, fmt, ...)					\
-	drm_dev_dbg((drm) ? (drm)->dev : NULL, DRM_UT_ATOMIC, fmt, ##__VA_ARGS__)
+	drm_dev_dbg(__drm_get_dev_ptr(drm), DRM_UT_ATOMIC, fmt, ##__VA_ARGS__)
 #define drm_dbg_vbl(drm, fmt, ...)					\
-	drm_dev_dbg((drm) ? (drm)->dev : NULL, DRM_UT_VBL, fmt, ##__VA_ARGS__)
+	drm_dev_dbg(__drm_get_dev_ptr(drm), DRM_UT_VBL, fmt, ##__VA_ARGS__)
 #define drm_dbg_state(drm, fmt, ...)					\
-	drm_dev_dbg((drm) ? (drm)->dev : NULL, DRM_UT_STATE, fmt, ##__VA_ARGS__)
+	drm_dev_dbg(__drm_get_dev_ptr(drm), DRM_UT_STATE, fmt, ##__VA_ARGS__)
 #define drm_dbg_lease(drm, fmt, ...)					\
-	drm_dev_dbg((drm) ? (drm)->dev : NULL, DRM_UT_LEASE, fmt, ##__VA_ARGS__)
+	drm_dev_dbg(__drm_get_dev_ptr(drm), DRM_UT_LEASE, fmt, ##__VA_ARGS__)
 #define drm_dbg_dp(drm, fmt, ...)					\
-	drm_dev_dbg((drm) ? (drm)->dev : NULL, DRM_UT_DP, fmt, ##__VA_ARGS__)
+	drm_dev_dbg(__drm_get_dev_ptr(drm), DRM_UT_DP, fmt, ##__VA_ARGS__)
 #define drm_dbg_drmres(drm, fmt, ...)					\
-	drm_dev_dbg((drm) ? (drm)->dev : NULL, DRM_UT_DRMRES, fmt, ##__VA_ARGS__)
+	drm_dev_dbg(__drm_get_dev_ptr(drm), DRM_UT_DRMRES, fmt, ##__VA_ARGS__)
 
 #define drm_dbg(drm, fmt, ...)	drm_dbg_driver(drm, fmt, ##__VA_ARGS__)
 
@@ -596,10 +613,9 @@ void __drm_err(const char *format, ...);
 #define __DRM_DEFINE_DBG_RATELIMITED(category, drm, fmt, ...)					\
 ({												\
 	static DEFINE_RATELIMIT_STATE(rs_, DEFAULT_RATELIMIT_INTERVAL, DEFAULT_RATELIMIT_BURST);\
-	const struct drm_device *drm_ = (drm);							\
 												\
 	if (drm_debug_enabled(DRM_UT_ ## category) && __ratelimit(&rs_))			\
-		drm_dev_printk(drm_ ? drm_->dev : NULL, KERN_DEBUG, fmt, ## __VA_ARGS__);	\
+		drm_dev_printk(__drm_get_dev_ptr(drm), KERN_DEBUG, fmt, ## __VA_ARGS__);	\
 })
 
 #define drm_dbg_kms_ratelimited(drm, fmt, ...) \
-- 
2.35.1