[PATCH -next 2/4] spi: mockup: Add writeable tracepoint for spi transfer

[Wei Yongjun]

Add writeable tracepoint for transfer_one_message(), then bpf program can
be used to control read and write data from spi master, 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, u8 tx_nbits, u8 rx_nbits)
  {
      if (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>
---
 drivers/spi/Kconfig               |  1 +
 drivers/spi/spi-mockup.c          | 50 +++++++++++++++++++++++++++++--
 include/linux/spi/spi-mockup.h    | 13 ++++++++
 include/trace/events/spi_mockup.h | 32 ++++++++++++++++++++
 4 files changed, 94 insertions(+), 2 deletions(-)

diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index b58a1bd7999d..e0f0fa2746ad 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -1161,6 +1161,7 @@ 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 06cf9d122d64..7a93b194ee53 100644
--- a/drivers/spi/spi-mockup.c
+++ b/drivers/spi/spi-mockup.c
@@ -13,6 +13,9 @@
 #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 {
@@ -149,13 +152,56 @@ static struct attribute *spi_mockup_attrs[] = {
 };
 ATTRIBUTE_GROUPS(spi_mockup);
 
+static int spi_mockup_transfer_writeable(struct spi_master *master,
+					 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));
+
+		if (t->tx_nbits)
+			memcpy(ctx->data, t->tx_buf, t->len);
+
+		trace_spi_transfer_writeable(ctx, msg->spi->chip_select, t->len,
+					     t->tx_nbits, t->rx_nbits);
+
+		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_master *master,
 			       struct spi_message *msg)
 {
-	msg->status = 0;
+	int ret = 0;
+
+	if (trace_spi_transfer_writeable_enabled())
+		ret = spi_mockup_transfer_writeable(master, msg);
+
+	msg->status = ret;
 	spi_finalize_current_message(master);
 
-	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..6a4fe88cb376
--- /dev/null
+++ b/include/linux/spi/spi-mockup.h
@@ -0,0 +1,13 @@
+/* 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;
+	__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..193302f8627a
--- /dev/null
+++ b/include/trace/events/spi_mockup.h
@@ -0,0 +1,32 @@
+/* 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,
+		 u8 tx_nbits, u8 rx_nbits),
+	TP_ARGS(msg, chip_select, len, tx_nbits, rx_nbits),
+	sizeof(struct spi_msg_ctx)
+);
+
+#endif /* _TRACE_SPI_MOCKUP_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
-- 
2.34.1