target: fix invalid fd error in transport layer

Return FdHandle by value instead of returning pointer to a local
object, which was going out of scope and causing invalid file
descriptor errors during CFAM read/write operations.

Also added temporary debug logs for demo; these will be removed
in a later cleanup commit.

Change-Id: I1476472b351dbdbdc98d59e9dc84bf740b90df9e

Author: devenrao

target/transport/transport.C

@@ -143,8 +143,8 @@ std::optional<FdHandle> fsiProbe(TARGETING::ConstTargetPtr target)
     return std::nullopt;
 }
 
-std::optional<FdHandle*> prepareCfamAccess(TARGETING::ConstTargetPtr target,
-                                           std::uint32_t addr)
+std::optional<FdHandle> prepareCfamAccess(TARGETING::ConstTargetPtr target,
+                                          std::uint32_t addr)
 {
     std::cout << "DEMO: transport prepareCfamAccess addr 0x" << std::hex << addr
               << " path " << getPhyPath(target) << "\n";
@@ -159,14 +159,16 @@ std::optional<FdHandle*> prepareCfamAccess(TARGETING::ConstTargetPtr target,
     }
 
     FdHandle& fd = *fdOpt;
+    std::cout << "DEMO:transport prepareCfamAcccess fd " << fd.get() << " off "
+              << off << std::endl;
     if (::lseek(fd.get(), off, SEEK_SET) < 0)
     {
         std::cerr << "CFAM lseek failed addr=0x" << std::hex << addr
                   << " errno=" << errno << " (" << strerror(errno) << ")\n";
         return std::nullopt;
     }
 
-    return &fd;
+    return std::move(fd);
 }
 
 std::optional<FdHandle> prepareScomAccess(TARGETING::ConstTargetPtr target,
@@ -230,14 +232,15 @@ int send_all(int fd, std::span<const std::byte> cmd)
 int getCfam(TARGETING::ConstTargetPtr target, std::uint32_t addr,
             std::uint32_t& value)
 {
-    auto fdPtrOpt = prepareCfamAccess(target, addr);
-    if (!fdPtrOpt)
+    auto fdOpt = prepareCfamAccess(target, addr);
+    if (!fdOpt)
     {
         return -1;
     }
-
-    FdHandle* fd = *fdPtrOpt;
-    if (::read(fd->get(), &value, sizeof(value)) < 0)
+    FdHandle& fd = *fdOpt;
+    std::cout << "DEMO transport: getCfam addr 0x" << std::hex << addr << " fd "
+              << fd.get() << std::endl;
+    if (::read(fd.get(), &value, sizeof(value)) < 0)
     {
         std::cerr << "getCfam read failed addr=0x" << std::hex << addr
                   << " errno=" << errno << " (" << strerror(errno) << ")\n";
@@ -253,15 +256,15 @@ int getCfam(TARGETING::ConstTargetPtr target, std::uint32_t addr,
 int putCfam(TARGETING::ConstTargetPtr target, std::uint32_t addr,
             std::uint32_t value)
 {
-    auto fdPtrOpt = prepareCfamAccess(target, addr);
-    if (!fdPtrOpt)
+    auto fdOpt = prepareCfamAccess(target, addr);
+    if (!fdOpt)
     {
         return -1;
     }
 
-    FdHandle* fd = *fdPtrOpt;
+    FdHandle& fd = *fdOpt;
     value = htobe32(value);
-    if (::write(fd->get(), &value, sizeof(value)) < 0)
+    if (::write(fd.get(), &value, sizeof(value)) < 0)
     {
         std::cerr << "putCfam write failed addr=0x" << std::hex << addr << "\n";
         return -1;