libdm: fetch and present device status flags

Fetch detailed information for devices through its flags and store in
helper Info class, i.e.:
- active
- access
- activeTable
- inactiveTable
- bufferFull

Change-Id: I3241c5bca00e038d19f99390f40710ca7cff8456
Bug: 137759376
Test: manual test
Signed-off-by: Alessio Balsini <balsini@google.com>

fs_mgr/libdm/dm.cpp

@@ -150,6 +150,15 @@ bool DeviceMapper::GetDeviceUniquePath(const std::string& name, std::string* pat
     return true;
 }
 
+std::optional<DeviceMapper::Info> DeviceMapper::GetDetailedInfo(const std::string& name) const {
+    struct dm_ioctl io;
+    InitIo(&io, name);
+    if (ioctl(fd_, DM_DEV_STATUS, &io) < 0) {
+        return std::nullopt;
+    }
+    return Info(io.flags);
+}
+
 DmDeviceState DeviceMapper::GetState(const std::string& name) const {
     struct dm_ioctl io;
     InitIo(&io, name);

fs_mgr/libdm/include/libdm/dm.h

@@ -27,6 +27,7 @@
 
 #include <chrono>
 #include <memory>
+#include <optional>
 #include <string>
 #include <utility>
 #include <vector>
@@ -70,10 +71,27 @@ class DeviceMapper final {
         uint64_t dev_;
     };
 
+    class Info {
+        uint32_t flags_;
+
+      public:
+        explicit Info(uint32_t flags) : flags_(flags) {}
+
+        bool IsActiveTablePresent() const { return flags_ & DM_ACTIVE_PRESENT_FLAG; }
+        bool IsBufferFull() const { return flags_ & DM_BUFFER_FULL_FLAG; }
+        bool IsInactiveTablePresent() const { return flags_ & DM_INACTIVE_PRESENT_FLAG; }
+        bool IsReadOnly() const { return flags_ & DM_READONLY_FLAG; }
+        bool IsSuspended() const { return flags_ & DM_SUSPEND_FLAG; }
+    };
+
     // Removes a device mapper device with the given name.
     // Returns 'true' on success, false otherwise.
     bool DeleteDevice(const std::string& name);
 
+    // Fetches and returns the complete state of the underlying device mapper
+    // device with given name.
+    std::optional<Info> GetDetailedInfo(const std::string& name) const;
+
     // Returns the current state of the underlying device mapper device
     // with given name.
     // One of INVALID, SUSPENDED or ACTIVE.