Revert "drm/printer: Allow NULL data in devcoredump printer"

This reverts commit f39aaded93.

drivers/gpu/drm/drm_print.c

@@ -78,9 +78,8 @@ void __drm_puts_coredump(struct drm_printer *p, const char *str)
 			copy = iterator->remain;
 
 		/* Copy out the bit of the string that we need */
-		if (iterator->data)
+		memcpy(iterator->data,
-			memcpy(iterator->data,
+			str + (iterator->start - iterator->offset), copy);
-			       str + (iterator->start - iterator->offset), copy);
 
 		iterator->offset = iterator->start + copy;
 		iterator->remain -= copy;
@@ -89,8 +88,7 @@ void __drm_puts_coredump(struct drm_printer *p, const char *str)
 
 		len = min_t(ssize_t, strlen(str), iterator->remain);
 
-		if (iterator->data)
+		memcpy(iterator->data + pos, str, len);
-			memcpy(iterator->data + pos, str, len);
 
 		iterator->offset += len;
 		iterator->remain -= len;
@@ -120,9 +118,8 @@ void __drm_printfn_coredump(struct drm_printer *p, struct va_format *vaf)
 	if ((iterator->offset >= iterator->start) && (len < iterator->remain)) {
 		ssize_t pos = iterator->offset - iterator->start;
 
-		if (iterator->data)
+		snprintf(((char *) iterator->data) + pos,
-			snprintf(((char *) iterator->data) + pos,
+			iterator->remain, "%pV", vaf);
-				 iterator->remain, "%pV", vaf);
 
 		iterator->offset += len;
 		iterator->remain -= len;

include/drm/drm_print.h

@@ -126,8 +126,7 @@ drm_vprintf(struct drm_printer *p, const char *fmt, va_list *va)
 
 /**
  * struct drm_print_iterator - local struct used with drm_printer_coredump
- * @data: Pointer to the devcoredump output buffer, can be NULL if using
+ * @data: Pointer to the devcoredump output buffer
- * drm_printer_coredump to determine size of devcoredump
  * @start: The offset within the buffer to start writing
  * @remain: The number of bytes to write for this iteration
  */
@@ -172,57 +171,6 @@ struct drm_print_iterator {
  *			coredump_read, ...)
  *	}
  *
- * The above example has a time complexity of O(N^2), where N is the size of the
- * devcoredump. This is acceptable for small devcoredumps but scales poorly for
- * larger ones.
- *
- * Another use case for drm_coredump_printer is to capture the devcoredump into
- * a saved buffer before the dev_coredump() callback. This involves two passes:
- * one to determine the size of the devcoredump and another to print it to a
- * buffer. Then, in dev_coredump(), copy from the saved buffer into the
- * devcoredump read buffer.
- *
- * For example::
- *
- *	char *devcoredump_saved_buffer;
- *
- *	ssize_t __coredump_print(char *buffer, ssize_t count, ...)
- *	{
- *		struct drm_print_iterator iter;
- *		struct drm_printer p;
- *
- *		iter.data = buffer;
- *		iter.start = 0;
- *		iter.remain = count;
- *
- *		p = drm_coredump_printer(&iter);
- *
- *		drm_printf(p, "foo=%d\n", foo);
- *		...
- *		return count - iter.remain;
- *	}
- *
- *	void coredump_print(...)
- *	{
- *		ssize_t count;
- *
- *		count = __coredump_print(NULL, INT_MAX, ...);
- *		devcoredump_saved_buffer = kvmalloc(count, GFP_KERNEL);
- *		__coredump_print(devcoredump_saved_buffer, count, ...);
- *	}
- *
- *	void coredump_read(char *buffer, loff_t offset, size_t count,
- *			   void *data, size_t datalen)
- *	{
- *		...
- *		memcpy(buffer, devcoredump_saved_buffer + offset, count);
- *		...
- *	}
- *
- * The above example has a time complexity of O(N*2), where N is the size of the
- * devcoredump. This scales better than the previous example for larger
- * devcoredumps.
- *
  * RETURNS:
  * The &drm_printer object
  */