stm class: dummy_stm: Add dummy driver for testing stm class

This is a simple module that pretends to be an stm device and discards
all the data that comes in. Useful for testing stm class and its users.

Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/hwtracing/stm/Kconfig

@@ -6,3 +6,11 @@ config STM
 	  Examples of such devices are Intel(R) Trace Hub and Coresight STM.
 
 	  Say Y here to enable System Trace Module device support.
+
+config STM_DUMMY
+	tristate "Dummy STM driver"
+	help
+	  This is a simple dummy device that pretends to be an stm device
+	  and discards your data. Use for stm class testing.
+
+	  If you don't know what this is, say N.

drivers/hwtracing/stm/Makefile

@@ -1,3 +1,5 @@
 obj-$(CONFIG_STM)	+= stm_core.o
 
 stm_core-y		:= core.o policy.o
+
+obj-$(CONFIG_STM_DUMMY)	+= dummy_stm.o

drivers/hwtracing/stm/dummy_stm.c

@@ -0,0 +1,66 @@
+/*
+ * A dummy STM device for stm/stm_source class testing.
+ * Copyright (c) 2014, Intel Corporation.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * STM class implements generic infrastructure for  System Trace Module devices
+ * as defined in MIPI STPv2 specification.
+ */
+
+#undef DEBUG
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/stm.h>
+
+static ssize_t
+dummy_stm_packet(struct stm_data *stm_data, unsigned int master,
+		 unsigned int channel, unsigned int packet, unsigned int flags,
+		 unsigned int size, const unsigned char *payload)
+{
+#ifdef DEBUG
+	u64 pl = 0;
+
+	if (payload)
+		pl = *(u64 *)payload;
+
+	if (size < 8)
+		pl &= (1ull << (size * 8)) - 1;
+	trace_printk("[%u:%u] [pkt: %x/%x] (%llx)\n", master, channel,
+		     packet, size, pl);
+#endif
+	return size;
+}
+
+static struct stm_data dummy_stm = {
+	.name		= "dummy_stm",
+	.sw_start	= 0x0000,
+	.sw_end		= 0xffff,
+	.sw_nchannels	= 0xffff,
+	.packet		= dummy_stm_packet,
+};
+
+static int dummy_stm_init(void)
+{
+	return stm_register_device(NULL, &dummy_stm, THIS_MODULE);
+}
+
+static void dummy_stm_exit(void)
+{
+	stm_unregister_device(&dummy_stm);
+}
+
+module_init(dummy_stm_init);
+module_exit(dummy_stm_exit);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("dummy_stm device");
+MODULE_AUTHOR("Alexander Shishkin <alexander.shishkin@linux.intel.com>");