[ndctl PATCH v2 2/6] libncdtl: Add initial support for NVDIMM_FAMILY_PAPR_SCM dimm family

[Vaibhav Jain <vaibhav@linux.ibm.com>]

Add necessary scaffolding in libndctl for dimms that support papr_scm
specification[1]. Since there can be platforms that support
Open-Firmware[2] but not the papr_scm specification, hence the changes
proposed first add support for probing if the dimm bus supports
Open-Firmware. This is done via querying for sysfs attribute 'of_node'
in dimm device sysfs directory. If available newly introduced member
'struct ndctl_bus.has_of_node' is set. During the probe of the dimm
and execution of add_dimm(), the newly introduced add_of_pmem_dimm()
is called if dimm bus reports supports Open-Firmware.

Function add_of_pmem_dimm() queries the 'compatible' device tree
attribute and based on its value assign NVDIMM_FAMILY_PAPR_SCM to the
dimm command family. In future, based on the contents of 'compatible'
attribute more of_pmem dimm families can be queried.

We also add support for parsing the dimm flags for
NVDIMM_FAMILY_PAPR_SCM supporting nvdimms as described at [3]. A newly
introduced function parse_papr_scm_flags() reads the contents of this
flag file and sets appropriate flag bits in 'struct
ndctl_dimm.flags'.

Also we advertise support for monitor mode by allocating a file
descriptor to the dimm 'flags' file and assigning it to 'struct
ndctl_dimm.health_event_fd'.

The dimm-ops implementation for NVDIMM_FAMILY_PAPR_SCM is
available in global variable 'papr_scm_dimm_ops' which points to
skeleton implementation in newly introduced file 'lib/papr_scm.c'.

References:
[1] Documentation/powerpc/papr_hcalls.rst
https://lore.kernel.org/linux-nvdimm/20200420070711.223545-2-vaibhav@linux.ibm.com/

[2] https://en.wikipedia.org/wiki/Open_Firmware

[3] Documentation/ABI/testing/sysfs-bus-papr-scm
https://lore.kernel.org/linux-nvdimm/20200420070711.223545-3-vaibhav@linux.ibm.com/

Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com>
---
Changelog:

v1..v2:
* Squashed the patch to parse dimm flags
* Updated the dimm flags parsing to add case for 'restore_fail' and
  'flush_fail'.
* Renamed parse_of_pmem_flags() to parse_papr_scm_flags().
* Updated the path to dimm flags file to 'papr/flags'.
* Introduced 'papr_scm.c' file in this patch rather than later in the
  patch series.
* Update add_of_pmem_dimm() to parse dimm flags and enable monitoring
  only if 'ibm,pmemory' compatible nvdimm is found.
---
 ndctl/lib/Makefile.am |  1 +
 ndctl/lib/libndctl.c  | 78 +++++++++++++++++++++++++++++++++++++++++++
 ndctl/lib/papr_scm.c  | 32 ++++++++++++++++++
 ndctl/lib/private.h   |  2 ++
 ndctl/libndctl.h      |  1 +
 ndctl/ndctl.h         |  1 +
 6 files changed, 115 insertions(+)
 create mode 100644 ndctl/lib/papr_scm.c

diff --git a/ndctl/lib/Makefile.am b/ndctl/lib/Makefile.am
index d6be5c3acd26..90ba680bee56 100644
--- a/ndctl/lib/Makefile.am
+++ b/ndctl/lib/Makefile.am
@@ -23,6 +23,7 @@ libndctl_la_SOURCES =\
 	hpe1.c \
 	msft.c \
 	hyperv.c \
+	papr_scm.c \
 	ars.c \
 	firmware.c \
 	libndctl.c \
diff --git a/ndctl/lib/libndctl.c b/ndctl/lib/libndctl.c
index d76dbf7e17de..60dad8e56f5a 100644
--- a/ndctl/lib/libndctl.c
+++ b/ndctl/lib/libndctl.c
@@ -799,6 +799,28 @@ static void parse_nfit_mem_flags(struct ndctl_dimm *dimm, char *flags)
 				ndctl_dimm_get_devname(dimm), flags);
 }
 
+static void parse_papr_scm_flags(struct ndctl_dimm *dimm, char *flags)
+{
+	char *start, *end;
+
+	start = flags;
+	while ((end = strchr(start, ' '))) {
+		*end = '\0';
+		if (strcmp(start, "not_armed") == 0)
+			dimm->flags.f_arm = 1;
+		else if (strcmp(start, "flush_fail") == 0)
+			dimm->flags.f_flush = 1;
+		else if (strcmp(start, "restore_fail") == 0)
+			dimm->flags.f_restore = 1;
+		else if (strcmp(start, "smart_notify") == 0)
+			dimm->flags.f_smart = 1;
+		start = end + 1;
+	}
+	if (end != start)
+		dbg(ndctl_dimm_get_ctx(dimm), "%s: %s\n",
+				ndctl_dimm_get_devname(dimm), flags);
+}
+
 static void parse_dimm_flags(struct ndctl_dimm *dimm, char *flags)
 {
 	char *start, *end;
@@ -856,6 +878,12 @@ static void *add_bus(void *parent, int id, const char *ctl_base)
 		bus->revision = strtoul(buf, NULL, 0);
 	}
 
+	sprintf(path, "%s/device/of_node/compatible", ctl_base);
+	if (sysfs_read_attr(ctx, path, buf) < 0)
+		bus->has_of_node = 0;
+	else
+		bus->has_of_node = 1;
+
 	sprintf(path, "%s/device/nfit/dsm_mask", ctl_base);
 	if (sysfs_read_attr(ctx, path, buf) < 0)
 		bus->nfit_dsm_mask = 0;
@@ -964,6 +992,10 @@ NDCTL_EXPORT int ndctl_bus_has_nfit(struct ndctl_bus *bus)
 	return bus->has_nfit;
 }
 
+NDCTL_EXPORT int ndctl_bus_has_of_node(struct ndctl_bus *bus)
+{
+	return bus->has_of_node;
+}
 /**
  * ndctl_bus_get_major - nd bus character device major number
  * @bus: ndctl_bus instance returned from ndctl_bus_get_{first|next}
@@ -1441,6 +1473,47 @@ static int ndctl_bind(struct ndctl_ctx *ctx, struct kmod_module *module,
 static int ndctl_unbind(struct ndctl_ctx *ctx, const char *devpath);
 static struct kmod_module *to_module(struct ndctl_ctx *ctx, const char *alias);
 
+static int add_of_pmem_dimm(struct ndctl_dimm *dimm, const char *dimm_base)
+{
+	int rc = -ENODEV;
+	char buf[SYSFS_ATTR_SIZE];
+	struct ndctl_ctx *ctx = dimm->bus->ctx;
+	char *path = calloc(1, strlen(dimm_base) + 100);
+
+	dbg(ctx, "Probing of_pmem dimm %d at %s\n", dimm->id, dimm_base);
+
+	if (!path)
+		return -ENOMEM;
+
+	sprintf(path, "%s/../of_node/compatible", dimm_base);
+	if (sysfs_read_attr(ctx, path, buf) < 0)
+		goto out;
+
+
+	dbg(ctx, "Compatible of_pmem dimm %d at %s\n", dimm->id, buf);
+	/* construct path to the papr compatible dimm flags file */
+	sprintf(path, "%s/papr/flags", dimm_base);
+
+	if (strcmp(buf, "ibm,pmemory") == 0 &&
+	    sysfs_read_attr(ctx, path, buf) == 0) {
+
+		dbg(ctx, "Found papr_scm dimm %d at %s\n", dimm->id, buf);
+		dimm->cmd_family = NVDIMM_FAMILY_PAPR_SCM;
+
+		/* Parse dimm flags */
+		parse_papr_scm_flags(dimm, buf);
+
+		/* Allocate monitor mode fd */
+		dimm->health_eventfd = open(path, O_RDONLY|O_CLOEXEC);
+		rc = 0;
+	}
+	/* Ignore dimm if unknown type */
+
+ out:
+	free(path);
+	return rc;
+}
+
 static int add_nfit_dimm(struct ndctl_dimm *dimm, const char *dimm_base)
 {
 	int i, rc = -1;
@@ -1619,6 +1692,8 @@ static void *add_dimm(void *parent, int id, const char *dimm_base)
 	if (ndctl_bus_has_nfit(bus)) {
 		dimm->formats = formats;
 		rc = add_nfit_dimm(dimm, dimm_base);
+	} else if (ndctl_bus_has_of_node(bus)) {
+		rc = add_of_pmem_dimm(dimm, dimm_base);
 	}
 
 	if (rc == -ENODEV) {
@@ -1636,6 +1711,9 @@ static void *add_dimm(void *parent, int id, const char *dimm_base)
 		dimm->ops = msft_dimm_ops;
 	if (dimm->cmd_family == NVDIMM_FAMILY_HYPERV)
 		dimm->ops = hyperv_dimm_ops;
+	if (dimm->cmd_family == NVDIMM_FAMILY_PAPR_SCM)
+		dimm->ops = papr_scm_dimm_ops;
+
  out:
 	if (rc) {
 		err(ctx, "Unable to probe dimm:%d. Err:%d\n", id, rc);
diff --git a/ndctl/lib/papr_scm.c b/ndctl/lib/papr_scm.c
new file mode 100644
index 000000000000..14ff8879f627
--- /dev/null
+++ b/ndctl/lib/papr_scm.c
@@ -0,0 +1,32 @@
+/*
+ * Copyright (C) 2020 IBM Corporation
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU Lesser General Public License,
+ * version 2.1, 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 Lesser General Public License for
+ * more details.
+ */
+#include <stdint.h>
+#include <stdlib.h>
+#include <limits.h>
+#include <util/log.h>
+#include <ndctl.h>
+#include <ndctl/libndctl.h>
+#include <lib/private.h>
+
+static bool papr_cmd_is_supported(struct ndctl_dimm *dimm, int cmd)
+{
+	/* Handle this separately to support monitor mode */
+	if (cmd == ND_CMD_SMART)
+		return true;
+
+	return !!(dimm->cmd_mask & (1ULL << cmd));
+}
+
+struct ndctl_dimm_ops * const papr_scm_dimm_ops = &(struct ndctl_dimm_ops) {
+	.cmd_is_supported = papr_cmd_is_supported,
+};
diff --git a/ndctl/lib/private.h b/ndctl/lib/private.h
index 2e537f0a8649..05c703ed71b4 100644
--- a/ndctl/lib/private.h
+++ b/ndctl/lib/private.h
@@ -167,6 +167,7 @@ struct ndctl_bus {
 	int dimms_init;
 	int regions_init;
 	int has_nfit;
+	int has_of_node;
 	char *bus_path;
 	char *bus_buf;
 	size_t buf_len;
@@ -352,6 +353,7 @@ extern struct ndctl_dimm_ops * const intel_dimm_ops;
 extern struct ndctl_dimm_ops * const hpe1_dimm_ops;
 extern struct ndctl_dimm_ops * const msft_dimm_ops;
 extern struct ndctl_dimm_ops * const hyperv_dimm_ops;
+extern struct ndctl_dimm_ops * const papr_scm_dimm_ops;
 
 static inline struct ndctl_bus *cmd_to_bus(struct ndctl_cmd *cmd)
 {
diff --git a/ndctl/libndctl.h b/ndctl/libndctl.h
index 2580f433ade8..daf11b8ce4ea 100644
--- a/ndctl/libndctl.h
+++ b/ndctl/libndctl.h
@@ -119,6 +119,7 @@ struct ndctl_bus *ndctl_bus_get_next(struct ndctl_bus *bus);
              bus = ndctl_bus_get_next(bus))
 struct ndctl_ctx *ndctl_bus_get_ctx(struct ndctl_bus *bus);
 int ndctl_bus_has_nfit(struct ndctl_bus *bus);
+int ndctl_bus_has_of_node(struct ndctl_bus *bus);
 unsigned int ndctl_bus_get_major(struct ndctl_bus *bus);
 unsigned int ndctl_bus_get_minor(struct ndctl_bus *bus);
 const char *ndctl_bus_get_devname(struct ndctl_bus *bus);
diff --git a/ndctl/ndctl.h b/ndctl/ndctl.h
index 008f81cdeb9f..426708e1fd9b 100644
--- a/ndctl/ndctl.h
+++ b/ndctl/ndctl.h
@@ -263,6 +263,7 @@ struct nd_cmd_pkg {
 #define NVDIMM_FAMILY_HPE2 2
 #define NVDIMM_FAMILY_MSFT 3
 #define NVDIMM_FAMILY_HYPERV 4
+#define NVDIMM_FAMILY_PAPR_SCM 5
 
 #define ND_IOCTL_CALL			_IOWR(ND_IOCTL, ND_CMD_CALL,\
 					struct nd_cmd_pkg)
-- 
2.25.3
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