kernel: allow reallocation of minor numbersHEADdevelop

3 files changed, 30 insertions, 1 deletions

diff --git a/kapi/kapi/devices/driver.hpp b/kapi/kapi/devices/driver.hpp
index 348e2841..20f66536 100644
--- a/kapi/kapi/devices/driver.hpp
+++ b/kapi/kapi/devices/driver.hpp
@@ -80,6 +80,11 @@ namespace kapi::devices
     //! Drivers that want to claim an auto-populated device node in devfs must override this function.
     [[nodiscard]] virtual auto claimed_major() const -> std::optional<std::uint8_t>;
 
+    //! Get the minor number associated with the driver and a device, if any.
+    //!
+    //! @param device The device associated with the relevant device number registration.
+    [[nodiscard]] virtual auto claimed_minor(device & device) const -> std::optional<std::uint8_t>;
+
     //! Get the name of this driver.
     //!
     //! @return The static name of this driver.
diff --git a/kernel/kapi/devices/driver.cpp b/kernel/kapi/devices/driver.cpp
index ee16b4c2..4f0ce0e4 100644
--- a/kernel/kapi/devices/driver.cpp
+++ b/kernel/kapi/devices/driver.cpp
@@ -12,6 +12,11 @@ namespace kapi::devices
     return std::nullopt;
   }
 
+  auto driver::claimed_minor(device &) const -> std::optional<std::uint8_t>
+  {
+    return std::nullopt;
+  }
+
   auto driver::query_facet(kapi::capabilities::facet_id) -> void *
   {
     return nullptr;
diff --git a/kernel/kernel/filesystem/device_number_registry.cpp b/kernel/kernel/filesystem/device_number_registry.cpp
index cced66e0..42663dba 100644
--- a/kernel/kernel/filesystem/device_number_registry.cpp
+++ b/kernel/kernel/filesystem/device_number_registry.cpp
@@ -9,6 +9,7 @@
 
 #include <kstd/memory.hpp>
 #include <kstd/mutex.hpp>
+#include <kstd/print.hpp>
 #include <kstd/result.hpp>
 #include <kstd/vector.hpp>
 
@@ -202,7 +203,25 @@ namespace kernel::filesystem
     {
       auto guard = kstd::lock_guard{m_lock};
 
-      auto minor = allocate_minor(binding->posix_type, *driver_major);
+      auto minor = std::uint8_t{};
+      auto driver_minor = driver->claimed_minor(*device);
+      if (driver_minor)
+      {
+        minor = *driver_minor;
+        auto filtered = std::views::filter(
+            m_entries, [&](auto e) { return e.type == binding->posix_type && e.number.major == *driver_major; });
+        auto found = std::ranges::find_if(filtered, [&](auto e) { return e.minor == minor; }, &entry::number);
+        if (found != std::ranges::cend(filtered))
+        {
+          kstd::println(kstd::print_sink::stderr, "[OS:DEV] Driver '{}' tried to claim duplicate minor {}",
+                        driver->name(), minor);
+          return;
+        }
+      }
+      else
+      {
+        minor = allocate_minor(binding->posix_type, *driver_major);
+      }
 
       numbered = entry{
         .number = {.major = *driver_major, .minor = minor},