Subject: [PATCH v2 09/15] spi: Use struct_size() helper

From: Andy Shevchenko <[email-masked]>
Date: Mon, 10 Jul 2023 18:49:26 +0300

Prefer struct_size() over open-coded versions.

Signed-off-by: Andy Shevchenko <[email-masked]>
---
 include/linux/spi/spi.h | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index c9479badf38c..9fb8efb068c6 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -17,6 +17,7 @@
 #include <linux/minmax.h>
 #include <linux/mod_devicetable.h>
 #include <linux/mutex.h>
+#include <linux/overflow.h>
 #include <linux/scatterlist.h>
 #include <linux/slab.h>
 #include <linux/smp.h>
@@ -1095,6 +1096,8 @@ struct spi_transfer {
  * @state: for use by whichever driver currently owns the message
  * @resources: for resource management when the spi message is processed
  * @prepared: spi_prepare_message was called for the this message
+ * @t: for use with spi_message_alloc() when message and transfers have
+ *	been allocated together
  *
  * A @spi_message is used to execute an atomic sequence of data transfers,
  * each represented by a struct spi_transfer.  The sequence is "atomic"
@@ -1147,6 +1150,9 @@ struct spi_message {
 
 	/* List of spi_res reources when the spi message is processed */
 	struct list_head        resources;
+
+	/* For embedding transfers into the memory of the message */
+	struct spi_transfer	t[];
 };
 
 static inline void spi_message_init_no_memset(struct spi_message *m)
@@ -1207,16 +1213,13 @@ static inline struct spi_message *spi_message_alloc(unsigned ntrans, gfp_t flags
 {
 	struct spi_message *m;
 
-	m = kzalloc(sizeof(struct spi_message)
-			+ ntrans * sizeof(struct spi_transfer),
-			flags);
+	m = kzalloc(struct_size(m, t, ntrans), flags);
 	if (m) {
 		unsigned i;
-		struct spi_transfer *t = (struct spi_transfer *)(m + 1);
 
 		spi_message_init_no_memset(m);
-		for (i = 0; i < ntrans; i++, t++)
-			spi_message_add_tail(t, m);
+		for (i = 0; i < ntrans; i++)
+			spi_message_add_tail(&m->t[i], m);
 	}
 	return m;
 }
-- 
2.40.0.1.gaa8946217a0b