File locking refactored (#631)

Remove FileMutex and wire locking into driver subsystems.

Platforms/platform-esp32/source/drivers/esp32_sdcard.cpp

@@ -3,6 +3,9 @@
 #include <tactility/driver.h>
 #include <tactility/drivers/esp32_sdcard.h>
 #include <tactility/drivers/esp32_sdspi.h>
+#include <tactility/drivers/spi_controller.h>
+
+#include <sdmmc_cmd.h>
 
 #include <soc/soc_caps.h>
 #if SOC_SDMMC_HOST_SUPPORTED
@@ -24,4 +27,78 @@ sdmmc_card_t* esp32_sdcard_get_card(Device* device) {
     return nullptr;
 }
 
+// No board in the tree has more than one SD-over-SPI card.
+static constexpr size_t MAX_BUS_LOCKS = 2;
+
+struct SdcardBusLock {
+    Device* sdcard = nullptr;      // owner, for removal
+    Device* controller = nullptr;  // parent SPI controller
+    int slot = 0;                  // sdspi_dev_handle_t, read back from card->host.slot
+    esp_err_t (*inner)(int, sdmmc_command_t*) = nullptr;
+};
+
+static SdcardBusLock bus_locks[MAX_BUS_LOCKS];
+
+static SdcardBusLock* find_by_slot(int slot) {
+    for (auto& entry : bus_locks) {
+        if (entry.sdcard != nullptr && entry.slot == slot) {
+            return &entry;
+        }
+    }
+    return nullptr;
+}
+
+static esp_err_t locked_do_transaction(int slot, sdmmc_command_t* cmd) {
+    const SdcardBusLock* entry = find_by_slot(slot);
+    if (entry == nullptr) {
+        return ESP_ERR_INVALID_STATE;
+    }
+    spi_controller_lock(entry->controller);
+    esp_err_t result = entry->inner(slot, cmd);
+    spi_controller_unlock(entry->controller);
+    return result;
+}
+
+error_t esp32_sdcard_install_bus_lock(Device* device, sdmmc_card_t* card) {
+    auto* parent = device_get_parent(device);
+    if (parent == nullptr || device_get_type(parent) != &SPI_CONTROLLER_TYPE) {
+        return ERROR_NONE;
+    }
+
+    if (card == nullptr) {
+        return ERROR_INVALID_STATE;
+    }
+
+    SdcardBusLock* slot_entry = nullptr;
+    for (auto& entry : bus_locks) {
+        if (entry.sdcard == nullptr) {
+            slot_entry = &entry;
+            break;
+        }
+    }
+    if (slot_entry == nullptr) {
+        return ERROR_OUT_OF_MEMORY;
+    }
+
+    slot_entry->sdcard = device;
+    slot_entry->controller = parent;
+    slot_entry->slot = card->host.slot;
+    slot_entry->inner = card->host.do_transaction;
+    card->host.do_transaction = locked_do_transaction;
+    return ERROR_NONE;
+}
+
+void esp32_sdcard_remove_bus_lock(Device* device) {
+    for (auto& entry : bus_locks) {
+        if (entry.sdcard == device) {
+            auto* card = esp32_sdcard_get_card(device);
+            if (card != nullptr) {
+                card->host.do_transaction = entry.inner;
+            }
+            entry = SdcardBusLock{};
+            return;
+        }
+    }
+}
+
 }