sandbox: spi: Add SPI emulation bus

This adds a SPI framework for people to hook up simulated SPI clients.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Simon Glass <sjg@chromium.org>

1 files changed, 58 insertions, 0 deletions

diff --git a/arch/sandbox/include/asm/spi.h b/arch/sandbox/include/asm/spi.h
new file mode 100644
index 0000000000..49b4a0f103
--- /dev/null
+++ b/arch/sandbox/include/asm/spi.h
@@ -0,0 +1,58 @@
+/*
+ * Simulate a SPI port and clients (see README.sandbox for details)
+ *
+ * Copyright (c) 2011-2013 The Chromium OS Authors.
+ * See file CREDITS for list of people who contributed to this
+ * project.
+ *
+ * Licensed under the GPL-2 or later.
+ */
+
+#ifndef __ASM_SPI_H__
+#define __ASM_SPI_H__
+
+#include <linux/types.h>
+
+/*
+ * The interface between the SPI bus and the SPI client.  The bus will
+ * instantiate a client, and that then call into it via these entry
+ * points.  These should be enough for the client to emulate the SPI
+ * device just like the real hardware.
+ */
+struct sandbox_spi_emu_ops {
+	/* The bus wants to instantiate a new client, so setup everything */
+	int (*setup)(void **priv, const char *spec);
+	/* The bus is done with us, so break things down */
+	void (*free)(void *priv);
+	/* The CS has been "activated" -- we won't worry about low/high */
+	void (*cs_activate)(void *priv);
+	/* The CS has been "deactivated" -- we won't worry about low/high */
+	void (*cs_deactivate)(void *priv);
+	/* The client is rx-ing bytes from the bus, so it should tx some */
+	int (*xfer)(void *priv, const u8 *rx, u8 *tx, uint bytes);
+};
+
+/*
+ * There are times when the data lines are allowed to tristate.  What
+ * is actually sensed on the line depends on the hardware.  It could
+ * always be 0xFF/0x00 (if there are pull ups/downs), or things could
+ * float and so we'd get garbage back.  This func encapsulates that
+ * scenario so we can worry about the details here.
+ */
+static inline void sandbox_spi_tristate(u8 *buf, uint len)
+{
+	/* XXX: make this into a user config option ? */
+	memset(buf, 0xff, len);
+}
+
+/*
+ * Extract the bus/cs from the spi spec and return the start of the spi
+ * client spec.  If the bus/cs are invalid for the current config, then
+ * it returns NULL.
+ *
+ * Example: arg="0:1:foo" will set bus to 0, cs to 1, and return "foo"
+ */
+const char *sandbox_spi_parse_spec(const char *arg, unsigned long *bus,
+				   unsigned long *cs);
+
+#endif