Merge pull request ARMmbed#57 from ARMmbed/g-trim

Remove erase in favor of trim

Author: Deepika

SDBlockDevice.cpp

@@ -147,13 +147,13 @@
 #include "mbed_debug.h"
 #include <errno.h>
 
-/* Required version: 5.5.4 and above */
+/* Required version: 5.6.1 and above */
 #ifdef MBED_MAJOR_VERSION
-#if (MBED_VERSION < MBED_ENCODE_VERSION(5,5,4))
+#if (MBED_VERSION < MBED_ENCODE_VERSION(5,6,1))
 #error "Incompatible mbed-os version detected! Required 5.5.4 and above"
 #endif
 #else
-#warning "mbed-os version 5.5.4 or above required"
+#warning "mbed-os version 5.6.1 or above required"
 #endif
 
 #define SD_COMMAND_TIMEOUT                       5000   /*!< Timeout in ms for response */
@@ -513,9 +513,17 @@ int SDBlockDevice::read(void *b, bd_addr_t addr, bd_size_t size)
     return status;
 }
 
-int SDBlockDevice::erase(bd_addr_t addr, bd_size_t size)
+bool SDBlockDevice::_is_valid_trim(bd_addr_t addr, bd_size_t size)
 {
-    if (!is_valid_erase(addr, size)) {
+    return (
+        addr % _erase_size == 0 &&
+        size % _erase_size == 0 &&
+        addr + size <= this->size());
+}
+
+int SDBlockDevice::trim(bd_addr_t addr, bd_size_t size)
+{
+    if (!_is_valid_trim(addr, size)) {
         return SD_BLOCK_DEVICE_ERROR_PARAMETER;
     }
 
@@ -526,15 +534,7 @@ int SDBlockDevice::erase(bd_addr_t addr, bd_size_t size)
     }
     int status = BD_ERROR_OK;
 
-    // Toss out erases that are too small, this is fine as the block device api
-    // doesn't garuntee the final state of erased bytes and a following program
-    // will still work fine.
-    if (size < _erase_size) {
-        _lock.unlock();
-        return status;
-    }
-
-    size -= _erase_size;
+    size -= _block_size;
     // SDSC Card (CCS=0) uses byte unit address
     // SDHC and SDXC Cards (CCS=1) use block unit address (512 Bytes unit)
     if (SDCARD_V2HC == _card_type) {
@@ -568,11 +568,6 @@ bd_size_t SDBlockDevice::get_program_size() const
     return _block_size;
 }
 
-bd_size_t SDBlockDevice::get_erase_size() const
-{
-    return _block_size;
-}
-
 bd_size_t SDBlockDevice::size() const
 {
     bd_size_t sectors = 0;

SDBlockDevice.h

@@ -85,15 +85,18 @@ class SDBlockDevice : public BlockDevice {
      */
     virtual int program(const void *buffer, bd_addr_t addr, bd_size_t size);
 
-    /** Erase blocks on a block device
+    /** Mark blocks as no longer in use
      *
-     *  The state of an erased block is undefined until it has been programmed
+     *  This function provides a hint to the underlying block device that a region of blocks
+     *  is no longer in use and may be erased without side effects. Erase must still be called
+     *  before programming, but trimming allows flash-translation-layers to schedule erases when
+     *  the device is not busy.
      *
-     *  @param addr     Address of block to begin erasing
-     *  @param size     Size to erase in bytes, must be a multiple of erase block size
+     *  @param addr     Address of block to mark as unused
+     *  @param size     Size to mark as unused in bytes, must be a multiple of erase block size
      *  @return         0 on success, negative error code on failure
      */
-    virtual int erase(bd_addr_t addr, bd_size_t size);
+    virtual int trim(bd_addr_t addr, bd_size_t size);
 
     /** Get the size of a readable block
      *
@@ -108,13 +111,6 @@ class SDBlockDevice : public BlockDevice {
      */
     virtual bd_size_t get_program_size() const;
 
-    /** Get the size of a eraseable block
-     *
-     *  @return         Size of a eraseable block in bytes
-     *  @note Must be a multiple of the program size
-     */
-    virtual bd_size_t get_erase_size() const;
-
     /** Get the total size of the underlying device
      *
      *  @return         Size of the underlying device in bytes
@@ -196,6 +192,8 @@ class SDBlockDevice : public BlockDevice {
     uint32_t _sectors;
     uint32_t _sd_sectors();
 
+    bool _is_valid_trim(bd_addr_t addr, bd_size_t size);
+
     /* SPI functions */
     Timer _spi_timer;               /**< Timer Class object used for busy wait */
     uint32_t _init_sck;             /**< Intial SPI frequency */