net/failsafe: add flexible device definition

Add the "exec" device type.
The parameters given to this type of device will be executed in a shell.
The output of this command is then used as a definition for a device.

That command can be re-interpreted if the related device is not
plugged-in. It allows for a device definition to react to system
changes (e.g. changing PCI bus for a given device).

Signed-off-by: Gaetan Rivet <gaetan.rivet@6wind.com>
Acked-by: Olga Shern <olgas@mellanox.com>

doc/guides/nics/fail_safe.rst

@@ -87,6 +87,19 @@ Fail-safe command line parameters
   additional sub-device parameters if need be. They will be passed on to the
   sub-device.
 
+- **exec(<shell command>)** parameter
+
+  This parameter allows the user to provide a command to the fail-safe PMD to
+  execute and define a sub-device.
+  It is done within a regular shell context.
+  The first line of its output is read by the fail-safe PMD and otherwise
+  interpreted as if passed by the regular **dev** parameter.
+  Any other line is discarded.
+  If the command fail or output an incorrect string, the sub-device is not
+  initialized.
+  All commas within the ``shell command`` are replaced by spaces before
+  executing the command. This helps using scripts to specify devices.
+
 - **mac** parameter [MAC address]
 
   This parameter allows the user to set a default MAC address to the fail-safe
@@ -134,6 +147,13 @@ This section shows some example of using **testpmd** with a fail-safe PMD.
          --vdev 'net_failsafe0,mac=de:ad:be:ef:01:02,dev(84:00.0),dev(net_ring0)'
          -w 81:00.0 -- -i
 
+#. Start testpmd using a flexible device definition
+
+   .. code-block:: console
+
+      $RTE_TARGET/build/app/testpmd -c 0xff -n 4 --no-pci \
+         --vdev='net_failsafe0,exec(echo 84:00.0)' -- -i
+
 Using the Fail-safe PMD from an application
 -------------------------------------------
 

drivers/net/failsafe/failsafe_args.c

@@ -34,6 +34,7 @@
 #include <string.h>
 #include <errno.h>
 
+#include <rte_debug.h>
 #include <rte_devargs.h>
 #include <rte_malloc.h>
 #include <rte_kvargs.h>
@@ -97,6 +98,72 @@ fs_parse_device(struct sub_device *sdev, char *args)
 	return 0;
 }
 
+static void
+fs_sanitize_cmdline(char *args)
+{
+	size_t len;
+
+	len = strnlen(args, DEVARGS_MAXLEN);
+	args[len - 1] = '\0';
+}
+
+static int
+fs_execute_cmd(struct sub_device *sdev, char *cmdline)
+{
+	FILE *fp;
+	/* store possible newline as well */
+	char output[DEVARGS_MAXLEN + 1];
+	size_t len;
+	int old_err;
+	int ret;
+
+	RTE_ASSERT(cmdline != NULL || sdev->cmdline != NULL);
+	if (sdev->cmdline == NULL) {
+		size_t i;
+
+		len = strlen(cmdline) + 1;
+		sdev->cmdline = calloc(1, len);
+		if (sdev->cmdline == NULL) {
+			ERROR("Command line allocation failed");
+			return -ENOMEM;
+		}
+		snprintf(sdev->cmdline, len, "%s", cmdline);
+		/* Replace all commas in the command line by spaces */
+		for (i = 0; i < len; i++)
+			if (sdev->cmdline[i] == ',')
+				sdev->cmdline[i] = ' ';
+	}
+	DEBUG("'%s'", sdev->cmdline);
+	old_err = errno;
+	fp = popen(sdev->cmdline, "r");
+	if (fp == NULL) {
+		ret = errno;
+		ERROR("popen: %s", strerror(errno));
+		errno = old_err;
+		return ret;
+	}
+	/* We only read one line */
+	if (fgets(output, sizeof(output) - 1, fp) == NULL) {
+		DEBUG("Could not read command output");
+		return -ENODEV;
+	}
+	fs_sanitize_cmdline(output);
+	ret = fs_parse_device(sdev, output);
+	if (ret) {
+		ERROR("Parsing device '%s' failed", output);
+		goto ret_pclose;
+	}
+ret_pclose:
+	ret = pclose(fp);
+	if (ret) {
+		ret = errno;
+		ERROR("pclose: %s", strerror(errno));
+		errno = old_err;
+		return ret;
+	}
+	return ret;
+}
+
 static int
 fs_parse_device_param(struct rte_eth_dev *dev, const char *param,
 		uint8_t head)
@@ -131,6 +198,14 @@ fs_parse_device_param(struct rte_eth_dev *dev, const char *param,
 		ret = fs_parse_device(sdev, args);
 		if (ret)
 			goto free_args;
+	} else if (strncmp(param, "exec", 4) == 0) {
+		ret = fs_execute_cmd(sdev, args);
+		if (ret == -ENODEV) {
+			DEBUG("Reading device info from command line failed");
+			ret = 0;
+		}
+		if (ret)
+			goto free_args;
 	} else {
 		ERROR("Unrecognized device type: %.*s", (int)b, param);
 		return -EINVAL;
@@ -328,6 +403,8 @@ failsafe_args_free(struct rte_eth_dev *dev)
 	uint8_t i;
 
 	FOREACH_SUBDEV(sdev, i, dev) {
+		rte_free(sdev->cmdline);
+		sdev->cmdline = NULL;
 		free(sdev->devargs.args);
 		sdev->devargs.args = NULL;
 	}
@@ -342,7 +419,8 @@ fs_count_device(struct rte_eth_dev *dev, const char *param,
 	while  (param[b] != '(' &&
 		param[b] != '\0')
 		b++;
-	if (strncmp(param, "dev", b) != 0) {
+	if (strncmp(param, "dev", b) != 0 &&
+	    strncmp(param, "exec", b) != 0) {
 		ERROR("Unrecognized device type: %.*s", (int)b, param);
 		return -EINVAL;
 	}
@@ -357,3 +435,21 @@ failsafe_args_count_subdevice(struct rte_eth_dev *dev,
 	return fs_parse_sub_devices(fs_count_device,
 				    dev, params);
 }
+
+int
+failsafe_args_parse_subs(struct rte_eth_dev *dev)
+{
+	struct sub_device *sdev;
+	uint8_t i;
+	int ret = 0;
+
+	FOREACH_SUBDEV(sdev, i, dev) {
+		if (sdev->state >= DEV_PARSED)
+			continue;
+		if (sdev->cmdline)
+			ret = fs_execute_cmd(sdev, sdev->cmdline);
+		if (ret == 0)
+			sdev->state = DEV_PARSED;
+	}
+	return 0;
+}

drivers/net/failsafe/failsafe_ether.c

@@ -188,6 +188,13 @@ failsafe_eth_dev_state_sync(struct rte_eth_dev *dev)
 	int ret;
 	uint8_t i;
 
+	if (PRIV(dev)->state < DEV_PARSED)
+		return 0;
+
+	ret = failsafe_args_parse_subs(dev);
+	if (ret)
+		return ret;
+
 	if (PRIV(dev)->state < DEV_PROBED)
 		return 0;
 	ret = failsafe_eal_init(dev);

drivers/net/failsafe/failsafe_private.h

@@ -44,6 +44,7 @@
 #define PMD_FAILSAFE_HOTPLUG_POLL_KVARG "hotplug_poll"
 #define PMD_FAILSAFE_PARAM_STRING	\
 	"dev(<ifc>),"			\
+	"exec(<shell command>),"	\
 	"mac=mac_addr,"			\
 	"hotplug_poll=u64"		\
 	""
@@ -87,6 +88,8 @@ struct sub_device {
 	struct rte_eth_dev *edev;
 	/* Device state machine */
 	enum dev_state state;
+	/* Some device are defined as a command line */
+	char *cmdline;
 };
 
 struct fs_priv {
@@ -135,6 +138,7 @@ uint16_t failsafe_tx_burst(void *txq,
 int failsafe_args_parse(struct rte_eth_dev *dev, const char *params);
 void failsafe_args_free(struct rte_eth_dev *dev);
 int failsafe_args_count_subdevice(struct rte_eth_dev *dev, const char *params);
+int failsafe_args_parse_subs(struct rte_eth_dev *dev);
 
 /* EAL */