[PATCH v2 -next 2/3] spi: mockup: Add writeable tracepoint for spi transfer

[Zhang Xiaoxu <zhangxiaoxu5@xxxxxxxxxx>]

From: Wei Yongjun <weiyongjun1@xxxxxxxxxx>

Add writeable tracepoint for transfer_one_message(), then bpf program
can be used to control read and write data from spi host, as mockup
chip's expectation.

For example:

  #include "vmlinux.h"
  #include <bpf/bpf_helpers.h>
  #include <bpf/bpf_tracing.h>

  SEC("raw_tp.w/spi_transfer_writeable")
  int BPF_PROG(spi_transfer_writeable_test, struct spi_msg_ctx *msg,
               u8 chip, unsigned int len)
  {
      if (msg->tx_nbits)
          msg->data[0] = 0x20;

      return 0;
  }

  char LICENSE[] SEC("license") = "GPL";

This will be useful for writing spi device mockup backend.

Signed-off-by: Wei Yongjun <weiyongjun1@xxxxxxxxxx>
Signed-off-by: Zhang Xiaoxu <zhangxiaoxu5@xxxxxxxxxx>
---
 drivers/spi/Kconfig               |  1 +
 drivers/spi/spi-mockup.c          | 52 +++++++++++++++++++++++++++++--
 include/linux/spi/spi-mockup.h    | 17 ++++++++++
 include/trace/events/spi_mockup.h | 31 ++++++++++++++++++
 4 files changed, 99 insertions(+), 2 deletions(-)
 create mode 100644 include/linux/spi/spi-mockup.h
 create mode 100644 include/trace/events/spi_mockup.h

diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index 1768e57f0088..608e224e52ef 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -1188,6 +1188,7 @@ config SPI_TLE62X0
 config SPI_MOCKUP
 	tristate "SPI controller Testing Driver"
 	depends on OF
+	select BPF_EVENTS
 	help
 	  This enables SPI controller testing driver, which provides a way to
 	  test SPI subsystem.
diff --git a/drivers/spi/spi-mockup.c b/drivers/spi/spi-mockup.c
index 4debfd1fb9fd..3835012e2ee8 100644
--- a/drivers/spi/spi-mockup.c
+++ b/drivers/spi/spi-mockup.c
@@ -14,6 +14,9 @@
 #include <linux/platform_device.h>
 #include <linux/spi/spi.h>
 
+#define CREATE_TRACE_POINTS
+#include <trace/events/spi_mockup.h>
+
 #define MOCKUP_CHIPSELECT_MAX		8
 
 struct mockup_spi {
@@ -150,13 +153,58 @@ static struct attribute *spi_mockup_attrs[] = {
 };
 ATTRIBUTE_GROUPS(spi_mockup);
 
+static int spi_mockup_transfer_writeable(struct spi_message *msg)
+{
+	struct spi_msg_ctx *ctx;
+	struct spi_transfer *t;
+	int ret = 0;
+
+	ctx = kmalloc(sizeof(*ctx), GFP_ATOMIC);
+	if (!ctx)
+		return -ENOMEM;
+
+	list_for_each_entry(t, &msg->transfers, transfer_list) {
+		if (t->len > SPI_BUFSIZ_MAX)
+			return -E2BIG;
+
+		memset(ctx, 0, sizeof(*ctx));
+		ctx->cs_off = t->cs_off;
+		ctx->cs_change = t->cs_change;
+		ctx->tx_nbits = t->tx_nbits;
+		ctx->rx_nbits = t->rx_nbits;
+
+		if (t->tx_nbits)
+			memcpy(ctx->data, t->tx_buf, t->len);
+
+		trace_spi_transfer_writeable(ctx, msg->spi->chip_select, t->len);
+
+		if (ctx->ret) {
+			ret = ctx->ret;
+			break;
+		}
+
+		if (t->rx_nbits)
+			memcpy(t->rx_buf, ctx->data, t->len);
+		msg->actual_length += t->len;
+	}
+
+	kfree(ctx);
+
+	return ret;
+}
+
 static int spi_mockup_transfer(struct spi_controller *ctrl,
 			       struct spi_message *msg)
 {
-	msg->status = 0;
+	int ret = 0;
+
+	if (trace_spi_transfer_writeable_enabled())
+		ret = spi_mockup_transfer_writeable(msg);
+
+	msg->status = ret;
 	spi_finalize_current_message(ctrl);
 
-	return 0;
+	return ret;
 }
 
 static int spi_mockup_probe(struct platform_device *pdev)
diff --git a/include/linux/spi/spi-mockup.h b/include/linux/spi/spi-mockup.h
new file mode 100644
index 000000000000..224894b416fb
--- /dev/null
+++ b/include/linux/spi/spi-mockup.h
@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef __LINUX_SPI_MOCKUP_H
+#define __LINUX_SPI_MOCKUP_H
+
+#define SPI_BUFSIZ_MAX		0x1000
+
+struct spi_msg_ctx {
+	int ret;
+	unsigned cs_off:1;
+	unsigned cs_change:1;
+	unsigned tx_nbits:3;
+	unsigned rx_nbits:3;
+	__u8 data[SPI_BUFSIZ_MAX];
+};
+
+#endif
diff --git a/include/trace/events/spi_mockup.h b/include/trace/events/spi_mockup.h
new file mode 100644
index 000000000000..46debf26a5e3
--- /dev/null
+++ b/include/trace/events/spi_mockup.h
@@ -0,0 +1,31 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * SPI mockup controller transfer writeable tracepoint
+ *
+ * Copyright(c) 2022 Huawei Technologies Co., Ltd.
+ */
+
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM spi_mockup
+
+#if !defined(_TRACE_SPI_MOCKUP_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_SPI_MOCKUP_H
+
+#include <linux/tracepoint.h>
+#include <linux/spi/spi-mockup.h>
+
+#ifndef DECLARE_TRACE_WRITABLE
+#define DECLARE_TRACE_WRITABLE(call, proto, args, size) \
+	DECLARE_TRACE(call, PARAMS(proto), PARAMS(args))
+#endif
+
+DECLARE_TRACE_WRITABLE(spi_transfer_writeable,
+	TP_PROTO(struct spi_msg_ctx *msg, u8 chip_select, unsigned int len),
+	TP_ARGS(msg, chip_select, len),
+	sizeof(struct spi_msg_ctx)
+);
+
+#endif /* _TRACE_SPI_MOCKUP_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
-- 
2.34.1