[ndctl PATCH 2/8] libndctl: Introduce a new dimm-ops dimm_init() & dimm_uninit()

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

There are scenarios when a dimm-provider need to allocate some
per-dimm data that can be quickly retrieved. This data can be used to
cache data that spans multiple 'struct ndctl_cmd' submissions.

Unfortunately currently in libnvdimm there is no easiy way to implement
this. Even if this data is some how store in an overloaded field of
'struct ndctl_dimm', managing its lifetime is a challenge.

To solve this problem this patch proposes a new member 'struct
ndctl_dimm.dimm_user_data' to store per-dimm data thats specific to a
dimm-provider. Also two new dimm-ops namely dimm_init() &
dimm_uninit() are introduced that can be used to manage the lifetime
of this per-dimm data.

Semantics
=========
int (*dimm_init)(struct ndctl_dimm *):

This callback will be called just after dimm-probe inside add_dimm()
is completed. Dimm-providers should use this callback to allocate
per-dimm data and assign it to 'struct ndctl_dimm.dimm_user_data'
member. In case this function returns an error, dimm initialization is
halted and errors out.

void (*dimm_uninit)(struct ndctl_dimm *):
This callback will be called during free_dimm() and is only called if
previous call to 'dimm_ops->dimm_init()' had reported no
error. Dimm-providers should use this callback to unallocate and
cleanup 'dimm_user_data'.

Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com>
---
 ndctl/lib/libndctl.c | 13 ++++++++++++-
 ndctl/lib/private.h  |  5 +++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/ndctl/lib/libndctl.c b/ndctl/lib/libndctl.c
index 38ddfea6dbc0..a5f5fdac9f48 100644
--- a/ndctl/lib/libndctl.c
+++ b/ndctl/lib/libndctl.c
@@ -596,6 +596,10 @@ static void free_dimm(struct ndctl_dimm *dimm)
 {
 	if (!dimm)
 		return;
+	/* If needed call the dimm uninitialization function */
+	if (dimm->ops && dimm->ops->dimm_uninit)
+		dimm->ops->dimm_uninit(dimm);
+
 	free(dimm->unique_id);
 	free(dimm->dimm_buf);
 	free(dimm->dimm_path);
@@ -1596,8 +1600,15 @@ 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;
- out:
+
+	/* Call the dimm initialization function if needed */
+	if (!rc && dimm->ops && dimm->ops->dimm_init)
+		rc = dimm->ops->dimm_init(dimm);
+
+out:
 	if (rc) {
+		/* Ensure dimm_uninit() is not called during free_dimm() */
+		dimm->ops = NULL;
 		err(ctx, "Unable to probe dimm:%d. Err:%d\n", id, rc);
 		goto err_read;
 	}
diff --git a/ndctl/lib/private.h b/ndctl/lib/private.h
index 1f6a01c55377..fb7fa47f1f37 100644
--- a/ndctl/lib/private.h
+++ b/ndctl/lib/private.h
@@ -98,6 +98,7 @@ struct ndctl_dimm {
 	} flags;
 	int locked;
 	int aliased;
+	void *dimm_user_data;
 	struct list_node list;
 	int formats;
 	int format[0];
@@ -340,6 +341,10 @@ struct ndctl_dimm_ops {
 	struct ndctl_cmd *(*new_ack_shutdown_count)(struct ndctl_dimm *);
 	int (*fw_update_supported)(struct ndctl_dimm *);
 	int (*xlat_firmware_status)(struct ndctl_cmd *);
+	/* Called just after dimm is initialized and probed */
+	int (*dimm_init)(struct ndctl_dimm *);
+	/* Called just before struct ndctl_dimm is de-allocated */
+	void (*dimm_uninit)(struct ndctl_dimm *);
 };
 
 struct ndctl_dimm_ops * const intel_dimm_ops;
-- 
2.24.1
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