Date:	Wed,  9 Jan 2013 18:31:09 +0100
From:	Lars-Peter Clausen <lars@...afoo.de>
To:	Grant Likely <grant.likely@...retlab.ca>
Cc:	Julia Lawall <Julia.Lawall@...6.fr>,
	spi-devel-general@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org, Jonathan Cameron <jic23@....ac.uk>,
	linux-iio@...r.kernel.org, Lars-Peter Clausen <lars@...afoo.de>
Subject: [PATCH 1/3] spi: Add helper functions for setting up transfers

Quite often the pattern used for setting up and transferring a synchronous SPI
transaction looks very much like the following:

	struct spi_message msg;
	struct spi_transfer xfers[] = {
		...
	};

	spi_message_init(&msg);
	spi_message_add_tail(&xfers[0], &msg);
	...
	spi_message_add_tail(&xfers[ARRAY_SIZE(xfers) - 1], &msg);

	ret = spi_sync(&msg);

This patch adds two new helper functions for handling this case. The first
helper function spi_message_init_with_transfers() takes a spi_message and an
array of spi_transfers. It will initialize the message and then call
spi_message_add_tail() for each transfer in the array. E.g. the following

	spi_message_init(&msg);
	spi_message_add_tail(&xfers[0], &msg);
	...
	spi_message_add_tail(&xfers[ARRAY_SIZE(xfers) - 1], &msg);

can be rewritten as

	spi_message_init_with_transfers(&msg, xfers, ARRAY_SIZE(xfers));

The second function spi_sync_transfer() takes a SPI device and an array of
spi_transfers. It will allocate a new spi_message (on the stack) and add all
transfers in the array to the message. Finally it will call spi_sync() on the
message.

E.g. the follwing

	struct spi_message msg;
	struct spi_transfer xfers[] = {
		...
	};

	spi_message_init(&msg);
	spi_message_add_tail(&xfers[0], &msg);
	...
	spi_message_add_tail(&xfers[ARRAY_SIZE(xfers) - 1], &msg);

	ret = spi_sync(spi, &msg);

can be rewritten as

	struct spi_transfer xfers[] = {
		...
	};

	ret = spi_sync_transfer(spi, xfers, ARRAY_SIZE(xfers));

The patch also adds a new cocci script which can detect such sequences as
described above and transform them automatically to use the new helper
functions.

Signed-off-by: Lars-Peter Clausen <lars@...afoo.de>

---
I'm not entirely happy with names of the two new functions and I'm open for
better suggestions.
---
 include/linux/spi/spi.h                        |  44 ++++++++
 scripts/coccinelle/api/spi_sync_transfer.cocci | 141 +++++++++++++++++++++++++
 2 files changed, 185 insertions(+)
 create mode 100644 scripts/coccinelle/api/spi_sync_transfer.cocci

diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index f629189..7dbe586 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -591,6 +591,26 @@ spi_transfer_del(struct spi_transfer *t)
 	list_del(&t->transfer_list);
 }
 
+/**
+ * spi_message_init_with_transfers - Initialize spi_message and append transfers
+ * @m: spi_message to be initialized
+ * @xfers: An array of spi transfers
+ * @num_xfers: Number of items in the xfer array
+ *
+ * This function initializes the given spi_message and adds each spi_transfer in
+ * the given array to the message.
+ */
+static inline void
+spi_message_init_with_transfers(struct spi_message *m,
+struct spi_transfer *xfers, unsigned int num_xfers)
+{
+	unsigned int i;
+
+	spi_message_init(m);
+	for (i = 0; i < num_xfers; ++i)
+		spi_message_add_tail(&xfers[i], m);
+}
+
 /* It's fine to embed message and transaction structures in other data
  * structures so long as you don't free them while they're in use.
  */
@@ -683,6 +703,30 @@ spi_read(struct spi_device *spi, void *buf, size_t len)
 	return spi_sync(spi, &m);
 }
 
+/**
+ * spi_sync_transfer - synchronous SPI data transfer
+ * @spi: device with which data will be exchanged
+ * @xfers: An array of spi_transfers
+ * @num_xfers: Number of items in the xfer array
+ * Context: can sleep
+ *
+ * Does a synchronous SPI data transfer of the given spi_transfer array.
+ *
+ * For more specific semantics see spi_sync().
+ *
+ * It returns zero on success, else a negative error code.
+ */
+static inline int
+spi_sync_transfer(struct spi_device *spi, struct spi_transfer *xfers,
+	unsigned int num_xfers)
+{
+	struct spi_message msg;
+
+	spi_message_init_with_transfers(&msg, xfers, num_xfers);
+
+	return spi_sync(spi, &msg);
+}
+
 /* this copies txbuf and rxbuf data; for small transfers only! */
 extern int spi_write_then_read(struct spi_device *spi,
 		const void *txbuf, unsigned n_tx,
diff --git a/scripts/coccinelle/api/spi_sync_transfer.cocci b/scripts/coccinelle/api/spi_sync_transfer.cocci
new file mode 100644
index 0000000..1e2efe3
--- /dev/null
+++ b/scripts/coccinelle/api/spi_sync_transfer.cocci
@@ -0,0 +1,141 @@
+///
+/// Use spi_sync_transfer instead of open-coding it
+///
+// Confidence: High
+// Options: --no-includes
+//
+// Keywords: spi_sync, spi_sync_transfer
+// Version min: 3.9
+//
+
+virtual context
+virtual patch
+virtual org
+virtual report
+
+@r1@
+identifier fn;
+identifier xfers;
+@@
+fn(...)
+{
+	...
+(
+	struct spi_transfer xfers[...];
+|
+	struct spi_transfer xfers[];
+)
+	...
+}
+
+@...ends on patch@
+identifier msg;
+expression spi;
+identifier r1.fn;
+identifier r1.xfers;
+@@
+fn(...)
+{
+...
+-struct spi_message msg;
+...
+-spi_message_init(&msg);
+<...
+-spi_message_add_tail(&xfers[...], &msg);
+...>
+
+-spi_sync(spi, &msg)
++spi_sync_transfer(spi, xfers, ARRAY_SIZE(xfers))
+...
+}
+
+@r3 depends on context || org || report@
+identifier msg;
+expression spi;
+identifier r1.xfers;
+identifier r1.fn;
+position p;
+@@
+fn(...)
+{
+...
+*struct spi_message msg;
+...
+*spi_message_init(&msg);
+<...
+*spi_message_add_tail(&xfers[...], &msg);
+...>
+*spi_sync@p(spi, &msg)
+...
+}
+
+@r2@
+identifier fn;
+identifier xfer;
+@@
+fn(...)
+{
+	...
+	struct spi_transfer xfer;
+	...
+}
+
+@...ends on patch@
+identifier msg;
+expression spi;
+identifier r2.xfer;
+identifier r2.fn;
+@@
+fn(...)
+{
+...
+-struct spi_message msg;
+...
+-spi_message_init(&msg);
+...
+-spi_message_add_tail(&xfer, &msg);
+...
+-spi_sync(spi, &msg)
++spi_sync_transfer(spi, &xfer, 1)
+...
+}
+
+@r4 depends on context || org || report@
+identifier msg;
+expression spi;
+identifier r2.xfer;
+identifier r2.fn;
+position p;
+@@
+fn(...)
+{
+...
+*struct spi_message msg;
+...
+*spi_message_init(&msg);
+...
+*spi_message_add_tail(&xfer, &msg);
+...
+*spi_sync@p(spi, &msg)
+...
+}
+
+@...ipt:python depends on report@
+p << r3.p;
+@@
+coccilib.report.print_report(p[0], "Consider using spi_sync_transfer instead of open-conding it.")
+
+@...ipt:python depends on report@
+p << r4.p;
+@@
+coccilib.report.print_report(p[0], "Consider using spi_sync_transfer instead of open-conding it.")
+
+@...ipt:python depends on org@
+p << r3.p;
+@@
+coccilib.org.print_todo(p[0], "Consider using spi_sync_transfer instead of open-conding it.")
+
+@...ipt:python depends on org@
+p << r4.p;
+@@
+coccilib.org.print_todo(p[0], "Consider using spi_sync_transfer instead of open-conding it.")
-- 
1.8.0

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