drm/i915: Add i915_param charp macro magic

Handling the dynamic charp module parameter requires us to copy it for
the error state, or remember to lock it when reading (in case it used
with 0600).

v2: Use __always_inline and __builtin_strcmp

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170221162619.15954-1-chris@chris-wilson.co.uk
Reviewed-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/i915_debugfs.c

@@ -72,6 +72,8 @@ static __always_inline void seq_print_param(struct seq_file *m,
 		seq_printf(m, "i915.%s=%d\n", name, *(const int *)x);
 	else if (!__builtin_strcmp(type, "unsigned int"))
 		seq_printf(m, "i915.%s=%u\n", name, *(const unsigned int *)x);
+	else if (!__builtin_strcmp(type, "char *"))
+		seq_printf(m, "i915.%s=%s\n", name, *(const char **)x);
 	else
 		BUILD_BUG();
 }

drivers/gpu/drm/i915/i915_gpu_error.c

@@ -557,6 +557,8 @@ static __always_inline void err_print_param(struct drm_i915_error_state_buf *m,
 		err_printf(m, "i915.%s=%d\n", name, *(const int *)x);
 	else if (!__builtin_strcmp(type, "unsigned int"))
 		err_printf(m, "i915.%s=%u\n", name, *(const unsigned int *)x);
+	else if (!__builtin_strcmp(type, "char *"))
+		err_printf(m, "i915.%s=%s\n", name, *(const char **)x);
 	else
 		BUILD_BUG();
 }
@@ -810,6 +812,12 @@ static void i915_error_object_free(struct drm_i915_error_object *obj)
 	kfree(obj);
 }
 
+static __always_inline void free_param(const char *type, void *x)
+{
+	if (!__builtin_strcmp(type, "char *"))
+		kfree(*(void **)x);
+}
+
 void __i915_gpu_state_free(struct kref *error_ref)
 {
 	struct i915_gpu_state *error =
@@ -840,6 +848,11 @@ void __i915_gpu_state_free(struct kref *error_ref)
 
 	kfree(error->overlay);
 	kfree(error->display);
+
+#define FREE(T, x) free_param(#T, &error->params.x);
+	I915_PARAMS_FOR_EACH(FREE);
+#undef FREE
+
 	kfree(error);
 }
 
@@ -1614,6 +1627,12 @@ static void i915_capture_gen_state(struct drm_i915_private *dev_priv,
 	       sizeof(error->device_info));
 }
 
+static __always_inline void dup_param(const char *type, void *x)
+{
+	if (!__builtin_strcmp(type, "char *"))
+		*(void **)x = kstrdup(*(void **)x, GFP_ATOMIC);
+}
+
 static int capture(void *data)
 {
 	struct i915_gpu_state *error = data;
@@ -1625,6 +1644,9 @@ static int capture(void *data)
 					   error->i915->gt.last_init_time));
 
 	error->params = i915;
+#define DUP(T, x) dup_param(#T, &error->params.x);
+	I915_PARAMS_FOR_EACH(DUP);
+#undef DUP
 
 	i915_capture_gen_state(error->i915, error);
 	i915_capture_reg_state(error->i915, error);