[PATCH 02/10] drm: drm_printer: Add printer for devcoredump

[Jordan Crouse <jcrouse-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>]

Add a drm printer suitable for use with the read callback for
devcoredump or any other file operation read() function that
isn't otherwise covered by seq_file.

Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
---
 drivers/gpu/drm/drm_print.c | 54 +++++++++++++++++++++++++++++++++++++
 include/drm/drm_print.h     | 27 +++++++++++++++++++
 2 files changed, 81 insertions(+)

diff --git a/drivers/gpu/drm/drm_print.c b/drivers/gpu/drm/drm_print.c
index 781518fd88e3..f6efde48f8b3 100644
--- a/drivers/gpu/drm/drm_print.c
+++ b/drivers/gpu/drm/drm_print.c
@@ -30,6 +30,60 @@
 #include <drm/drmP.h>
 #include <drm/drm_print.h>
 
+void __drm_printfn_coredump(struct drm_printer *p, struct va_format *vaf)
+{
+	struct drm_print_iterator *iterator = p->arg;
+
+	ssize_t len;
+
+	if (!iterator->remain)
+		return;
+
+	if (iterator->offset < iterator->start) {
+		char *buf;
+		ssize_t copy;
+
+		/* Figure out how big the string will be */
+		len = snprintf(NULL, 0, "%pV", vaf);
+
+		if (iterator->offset + len <= iterator->start) {
+			iterator->offset += len;
+			return;
+		}
+
+		/* Print the string into a temporary buffer */
+		buf = kmalloc(len + 1,
+			GFP_KERNEL | __GFP_NOWARN | __GFP_NORETRY);
+		if (!buf)
+			return;
+
+		snprintf(buf, len + 1, "%pV", vaf);
+
+		copy = len - (iterator->start - iterator->offset);
+
+		if (copy > iterator->remain)
+			copy = iterator->remain;
+
+		/* Copy out the bit of the string that we need */
+		memcpy(iterator->data,
+			buf + (iterator->start - iterator->offset), copy);
+
+		iterator->offset = iterator->start + copy;
+		iterator->remain -= copy;
+
+		kfree(buf);
+	} else {
+		ssize_t pos = iterator->offset - iterator->start;
+
+		len = scnprintf(((char *) iterator->data) + pos,
+			iterator->remain, "%pV", vaf);
+
+		iterator->offset += len;
+		iterator->remain -= len;
+	}
+}
+EXPORT_SYMBOL(__drm_printfn_coredump);
+
 void __drm_printfn_seq_file(struct drm_printer *p, struct va_format *vaf)
 {
 	seq_printf(p->arg, "%pV", vaf);
diff --git a/include/drm/drm_print.h b/include/drm/drm_print.h
index 2a4a42e59a47..29eee5175eac 100644
--- a/include/drm/drm_print.h
+++ b/include/drm/drm_print.h
@@ -73,6 +73,7 @@ struct drm_printer {
 	const char *prefix;
 };
 
+void __drm_printfn_coredump(struct drm_printer *p, struct va_format *vaf);
 void __drm_printfn_seq_file(struct drm_printer *p, struct va_format *vaf);
 void __drm_printfn_info(struct drm_printer *p, struct va_format *vaf);
 void __drm_printfn_debug(struct drm_printer *p, struct va_format *vaf);
@@ -104,6 +105,32 @@ drm_vprintf(struct drm_printer *p, const char *fmt, va_list *va)
 #define drm_printf_indent(printer, indent, fmt, ...) \
 	drm_printf((printer), "%.*s" fmt, (indent), "\t\t\t\t\tX", ##__VA_ARGS__)
 
+struct drm_print_iterator {
+	void *data;
+
+	ssize_t start;
+	ssize_t offset;
+	ssize_t remain;
+};
+
+/**
+ * drm_coredump_printer - construct a &drm_printer that can output to a buffer
+ * from the read function for devcoredump
+ * @iter: A pointer to a struct drm_print_iterator for the read instance
+ *
+ * RETURNS:
+ * The &drm_printer object
+ */
+static inline struct drm_printer
+drm_coredump_printer(struct drm_print_iterator *iter)
+{
+	struct drm_printer p = {
+		.printfn = __drm_printfn_coredump,
+		.arg = iter,
+	};
+	return p;
+}
+
 /**
  * drm_seq_file_printer - construct a &drm_printer that outputs to &seq_file
  * @f:  the &struct seq_file to output to
-- 
2.17.0

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