pstore/blk: Support non-block storage devices

Add support for non-block devices (e.g. MTD). A non-block driver calls
pstore_blk_register_device() to register iself.

In addition, pstore/zone is updated to handle non-block devices,
where an erase must be done before a write. Without this, there is no
way to remove records stored to an MTD.

Signed-off-by: WeiXiong Liao <liaoweixiong@allwinnertech.com>
Link: https://lore.kernel.org/lkml/20200511233229.27745-10-keescook@chromium.org/
Co-developed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>

2 files changed, 44 insertions, 0 deletions

diff --git a/include/linux/pstore_blk.h b/include/linux/pstore_blk.h
index 0c40774e71e0..61e914522b01 100644
--- a/include/linux/pstore_blk.h
+++ b/include/linux/pstore_blk.h
@@ -50,6 +50,44 @@ int  register_pstore_blk(struct pstore_blk_info *info);
 void unregister_pstore_blk(unsigned int major);
 
 /**
+ * struct pstore_device_info - back-end pstore/blk driver structure.
+ *
+ * @total_size: The total size in bytes pstore/blk can use. It must be greater
+ *		than 4096 and be multiple of 4096.
+ * @flags:	Refer to macro starting with PSTORE_FLAGS defined in
+ *		linux/pstore.h. It means what front-ends this device support.
+ *		Zero means all backends for compatible.
+ * @read:	The general read operation. Both of the function parameters
+ *		@size and @offset are relative value to bock device (not the
+ *		whole disk).
+ *		On success, the number of bytes should be returned, others
+ *		means error.
+ * @write:	The same as @read, but the following error number:
+ *		-EBUSY means try to write again later.
+ *		-ENOMSG means to try next zone.
+ * @erase:	The general erase operation for device with special removing
+ *		job. Both of the function parameters @size and @offset are
+ *		relative value to storage.
+ *		Return 0 on success and others on failure.
+ * @panic_write:The write operation only used for panic case. It's optional
+ *		if you do not care panic log. The parameters are relative
+ *		value to storage.
+ *		On success, the number of bytes should be returned, others
+ *		excluding -ENOMSG mean error. -ENOMSG means to try next zone.
+ */
+struct pstore_device_info {
+	unsigned long total_size;
+	unsigned int flags;
+	pstore_zone_read_op read;
+	pstore_zone_write_op write;
+	pstore_zone_erase_op erase;
+	pstore_zone_write_op panic_write;
+};
+
+int  register_pstore_device(struct pstore_device_info *dev);
+void unregister_pstore_device(struct pstore_device_info *dev);
+
+/**
  * struct pstore_blk_config - the pstore_blk backend configuration
  *
  * @device:		Name of the desired block device
diff --git a/include/linux/pstore_zone.h b/include/linux/pstore_zone.h
index e79a18e41064..1e35eaa33e5e 100644
--- a/include/linux/pstore_zone.h
+++ b/include/linux/pstore_zone.h
@@ -7,6 +7,7 @@
 
 typedef ssize_t (*pstore_zone_read_op)(char *, size_t, loff_t);
 typedef ssize_t (*pstore_zone_write_op)(const char *, size_t, loff_t);
+typedef ssize_t (*pstore_zone_erase_op)(size_t, loff_t);
 /**
  * struct pstore_zone_info - pstore/zone back-end driver structure
  *
@@ -27,6 +28,10 @@ typedef ssize_t (*pstore_zone_write_op)(const char *, size_t, loff_t);
  * @write:	The same as @read, but the following error number:
  *		-EBUSY means try to write again later.
  *		-ENOMSG means to try next zone.
+ * @erase:	The general erase operation for device with special removing
+ *		job. Both of the function parameters @size and @offset are
+ *		relative value to storage.
+ *		Return 0 on success and others on failure.
  * @panic_write:The write operation only used for panic case. It's optional
  *		if you do not care panic log. The parameters are relative
  *		value to storage.
@@ -45,6 +50,7 @@ struct pstore_zone_info {
 	unsigned long ftrace_size;
 	pstore_zone_read_op read;
 	pstore_zone_write_op write;
+	pstore_zone_erase_op erase;
 	pstore_zone_write_op panic_write;
 };