[PATCH v6 01/10] drm/print: Fix and add support for NULL as first argument in drm_* macros

[Siddh Raman Pant]

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.

Also, add support for NULL in __drm_printk, so that all the
drm_* macros will hence support NULL as the first argument.
This also means that deprecation comments mentioning pr_()*
can now be changed to the drm equivalents.

There is a need to support device pointers, as in some cases,
we may not have drm_device but just the device ptr, such as
when dealing with struct mipi_dsi_host. Before this change,
passing just mipi_dsi_host would have worked, since due to
preprocessing, the resultant would be "host->dev", but now
due to NULL check that cannot happen.

Signed-off-by: Siddh Raman Pant <code@xxxxxxxx>
---
 include/drm/drm_print.h | 114 ++++++++++++++++++++++++++++++----------
 1 file changed, 87 insertions(+), 27 deletions(-)

diff --git a/include/drm/drm_print.h b/include/drm/drm_print.h
index a44fb7ef257f..481bf129cc39 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;
@@ -445,15 +446,73 @@ void __drm_dev_dbg(struct _ddebug *desc, const struct device *dev,
 #define DRM_DEV_DEBUG_KMS(dev, fmt, ...)				\
 	drm_dev_dbg(dev, DRM_UT_KMS, fmt, ##__VA_ARGS__)
 
+/* Helpers for struct drm_device based logging. */
+
+/**
+ * __drm_dev_ptr - Helper function to get drm->dev pointer.
+ * @drm: struct drm_device pointer.
+ *
+ * RETURNS:
+ * The struct device pointer (NULL if @drm is NULL).
+ */
+static inline struct device *__drm_dev_ptr(const struct drm_device *drm)
+{
+	if (drm)
+		return drm->dev;
+
+	return NULL;
+}
+
+/**
+ * __dev_ptr - Helper function to get the same device pointer.
+ * @dev: struct device pointer, or NULL.
+ *
+ * RETURNS:
+ * The struct device pointer (NULL if @dev is NULL).
+ */
+static inline struct device *__dev_ptr(const struct device *dev)
+{
+	return (struct device *)dev;
+}
+
+/**
+ * __get_dev_ptr - Helper to get device pointer given struct drm_device *,
+ *		   or struct device *, or NULL.
+ *
+ * Primarily for use in drm_*() print macros, since they need to handle NULL
+ * as the first argument passed.
+ *
+ * struct device pointers are supported for edge cases (such as mipi_dsi_host),
+ * the default (and recommended) way is to pass struct drm_device pointer.
+ */
+#define  __get_dev_ptr(drm)			\
+	_Generic((drm),				\
+		struct device * :		\
+			__dev_ptr,		\
+		const struct device * :		\
+			__dev_ptr,		\
+		default :			\
+			__drm_dev_ptr		\
+	)(drm)
+
 /*
  * struct drm_device based logging
  *
  * Prefer drm_device based logging over device or prink based logging.
+ *
+ * The below macros support device pointers to cope for edge cases where
+ * we only have device (like in mipi_dsi_host) but not drm_device.
  */
 
 /* Helper for struct drm_device based logging. */
 #define __drm_printk(drm, level, type, fmt, ...)			\
-	dev_##level##type((drm)->dev, "[drm] " fmt, ##__VA_ARGS__)
+({									\
+	struct device *__dev_ = __get_dev_ptr(drm);			\
+	if (__dev_)							\
+		dev_##level##type(__dev_, "[drm] " fmt, ##__VA_ARGS__);	\
+	else								\
+		pr_##level##type("[drm] " fmt, ##__VA_ARGS__);		\
+})
 
 
 #define drm_info(drm, fmt, ...)					\
@@ -487,25 +546,25 @@ 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(__get_dev_ptr(drm), DRM_UT_CORE, fmt, ##__VA_ARGS__)
+#define drm_dbg_driver(drm, fmt, ...)					\
+	drm_dev_dbg(__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(__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(__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(__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(__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(__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(__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(__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(__get_dev_ptr(drm), DRM_UT_DRMRES, fmt, ##__VA_ARGS__)
 
 #define drm_dbg(drm, fmt, ...)	drm_dbg_driver(drm, fmt, ##__VA_ARGS__)
 
@@ -533,31 +592,31 @@ void __drm_err(const char *format, ...);
 #define _DRM_PRINTK(once, level, fmt, ...)				\
 	printk##once(KERN_##level "[" DRM_NAME "] " fmt, ##__VA_ARGS__)
 
-/* NOTE: this is deprecated in favor of pr_info(). */
+/* NOTE: this is deprecated in favor of drm_info(NULL, ...). */
 #define DRM_INFO(fmt, ...)						\
 	_DRM_PRINTK(, INFO, fmt, ##__VA_ARGS__)
-/* NOTE: this is deprecated in favor of pr_notice(). */
+/* NOTE: this is deprecated in favor of drm_notice(NULL, ...). */
 #define DRM_NOTE(fmt, ...)						\
 	_DRM_PRINTK(, NOTICE, fmt, ##__VA_ARGS__)
-/* NOTE: this is deprecated in favor of pr_warn(). */
+/* NOTE: this is deprecated in favor of drm_warn(NULL, ...). */
 #define DRM_WARN(fmt, ...)						\
 	_DRM_PRINTK(, WARNING, fmt, ##__VA_ARGS__)
 
-/* NOTE: this is deprecated in favor of pr_info_once(). */
+/* NOTE: this is deprecated in favor of drm_info_once(NULL, ...). */
 #define DRM_INFO_ONCE(fmt, ...)						\
 	_DRM_PRINTK(_once, INFO, fmt, ##__VA_ARGS__)
-/* NOTE: this is deprecated in favor of pr_notice_once(). */
+/* NOTE: this is deprecated in favor of drm_notice_once(NULL, ...). */
 #define DRM_NOTE_ONCE(fmt, ...)						\
 	_DRM_PRINTK(_once, NOTICE, fmt, ##__VA_ARGS__)
-/* NOTE: this is deprecated in favor of pr_warn_once(). */
+/* NOTE: this is deprecated in favor of drm_warn_once(NULL, ...). */
 #define DRM_WARN_ONCE(fmt, ...)						\
 	_DRM_PRINTK(_once, WARNING, fmt, ##__VA_ARGS__)
 
-/* NOTE: this is deprecated in favor of pr_err(). */
+/* NOTE: this is deprecated in favor of drm_err(NULL, ...). */
 #define DRM_ERROR(fmt, ...)						\
 	__drm_err(fmt, ##__VA_ARGS__)
 
-/* NOTE: this is deprecated in favor of pr_err_ratelimited(). */
+/* NOTE: this is deprecated in favor of drm_err_ratelimited(NULL, ...). */
 #define DRM_ERROR_RATELIMITED(fmt, ...)					\
 	DRM_DEV_ERROR_RATELIMITED(NULL, fmt, ##__VA_ARGS__)
 
@@ -593,13 +652,14 @@ void __drm_err(const char *format, ...);
 #define DRM_DEBUG_DP(fmt, ...)						\
 	__drm_dbg(DRM_UT_DP, fmt, ## __VA_ARGS__)
 
-#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__);	\
+#define __DRM_DEFINE_DBG_RATELIMITED(category, drm, fmt, ...)		\
+({									\
+	static DEFINE_RATELIMIT_STATE(rs_, DEFAULT_RATELIMIT_INTERVAL,	\
+				      DEFAULT_RATELIMIT_BURST);		\
+									\
+	if (drm_debug_enabled(DRM_UT_ ## category) && __ratelimit(&rs_))\
+		drm_dev_printk(__get_dev_ptr(drm), KERN_DEBUG,		\
+			       fmt, ## __VA_ARGS__);			\
 })
 
 #define drm_dbg_kms_ratelimited(drm, fmt, ...) \
-- 
2.39.0