mtd: re-add mtd_write_page()

Add a write_page() command that performs a read-modify-write cycle
if necessary.

drivers/include/mtd.h

@@ -60,8 +60,16 @@ typedef struct {
     uint32_t sector_count;     /**< Number of sector in the MTD */
     uint32_t pages_per_sector; /**< Number of pages by sector in the MTD */
     uint32_t page_size;        /**< Size of the pages in the MTD */
+#if defined(MODULE_MTD_WRITE_PAGE) || DOXYGEN
+    void *work_area;           /**< sector-sized buffer */
+#endif
 } mtd_dev_t;
 
+/**
+ * @brief   MTD driver can write any data to the storage without erasing it first.
+ */
+#define MTD_DRIVER_FLAG_DIRECT_WRITE    (1 << 0)
+
 /**
  * @brief   MTD driver interface
  *
@@ -203,6 +211,11 @@ struct mtd_desc {
      * @return < 0 value on error
      */
     int (*power)(mtd_dev_t *dev, enum mtd_power_state power);
+
+    /**
+     * @brief   Properties of the MTD driver
+     */
+    uint8_t flags;
 };
 
 /**
@@ -306,6 +319,36 @@ int mtd_write(mtd_dev_t *mtd, const void *src, uint32_t addr, uint32_t count);
 int mtd_write_page_raw(mtd_dev_t *mtd, const void *src, uint32_t page,
                        uint32_t offset, uint32_t size);
 
+/**
+ * @brief   Write data to a MTD device with pagewise addressing
+ *
+ * The MTD layer will take care of splitting up the transaction into multiple
+ * writes if it is required by the underlying storage media.
+ *
+ * If the underlying sector needs to be erased before it can be written, the MTD
+ * layer will take care of the read-modify-write operation.
+ *
+ * @p offset must be smaller than the page size
+ *
+ * @note this requires the `mtd_write_page` module
+ *
+ * @param      mtd      the device to write to
+ * @param[in]  src      the buffer to write
+ * @param[in]  page     Page number to start writing to
+ * @param[in]  offset   byte offset from the start of the page
+ * @param[in]  size     the number of bytes to write
+ *
+ * @return 0 on success
+ * @return < 0 if an error occurred
+ * @return -ENODEV if @p mtd is not a valid device
+ * @return -ENOTSUP if operation is not supported on @p mtd
+ * @return -EOVERFLOW if @p addr or @p count are not valid, i.e. outside memory,
+ * @return -EIO if I/O error occurred
+ * @return -EINVAL if parameters are invalid
+ */
+int mtd_write_page(mtd_dev_t *mtd, const void *src, uint32_t page,
+                   uint32_t offset, uint32_t size);
+
 /**
  * @brief   Erase sectors of a MTD device
  *

drivers/mtd/mtd.c

@@ -22,6 +22,8 @@
 #include <errno.h>
 #include <limits.h>
 #include <stddef.h>
+#include <stdlib.h>
+#include <string.h>
 
 #include "bitarithm.h"
 #include "mtd.h"
@@ -32,12 +34,22 @@ int mtd_init(mtd_dev_t *mtd)
         return -ENODEV;
     }
 
+    int res = -ENOTSUP;
+
     if (mtd->driver->init) {
-        return mtd->driver->init(mtd);
+        res = mtd->driver->init(mtd);
     }
-    else {
+
-        return -ENOTSUP;
+#ifdef MODULE_MTD_WRITE_PAGE
+    if ((mtd->driver->flags & MTD_DRIVER_FLAG_DIRECT_WRITE) == 0) {
+        mtd->work_area = malloc(mtd->pages_per_sector * mtd->page_size);
+        if (mtd->work_area == NULL) {
+            res = -ENOMEM;
+        }
     }
+#endif
+
+    return res;
 }
 
 int mtd_read(mtd_dev_t *mtd, void *dest, uint32_t addr, uint32_t count)
@@ -125,6 +137,44 @@ int mtd_write(mtd_dev_t *mtd, const void *src, uint32_t addr, uint32_t count)
     return mtd_write_page_raw(mtd, src, addr >> page_shift, addr & page_mask, count);
 }
 
+#ifdef MODULE_MTD_WRITE_PAGE
+int mtd_write_page(mtd_dev_t *mtd, const void *data, uint32_t page,
+                   uint32_t offset, uint32_t len)
+{
+    if (!mtd || !mtd->driver) {
+        return -ENODEV;
+    }
+
+    if (mtd->work_area == NULL) {
+        return mtd_write_page_raw(mtd, data, page, offset, len);
+    }
+
+    int res;
+    uint8_t *work = mtd->work_area;
+    const uint32_t sector = page / mtd->pages_per_sector;
+    const uint32_t sector_page = sector * mtd->pages_per_sector;
+    const uint32_t sector_size = mtd->pages_per_sector * mtd->page_size;
+
+    /* copy sector to RAM */
+    res = mtd_read_page(mtd, work, sector_page, 0, sector_size);
+    if (res < 0) {
+        return res;
+    }
+
+    /* erase sector */
+    res = mtd_erase_sector(mtd, sector, 1);
+    if (res < 0) {
+        return res;
+    }
+
+    /* modify sector in RAM */
+    memcpy(work + (page - sector_page) * mtd->page_size + offset, data, len);
+
+    /* write back modified sector copy */
+    return mtd_write_page_raw(mtd, work, sector_page, 0, sector_size);
+}
+#endif
+
 int mtd_write_page_raw(mtd_dev_t *mtd, const void *src, uint32_t page, uint32_t offset,
                        uint32_t count)
 {

makefiles/pseudomodules.inc.mk

@@ -81,6 +81,7 @@ PSEUDOMODULES += log_color
 PSEUDOMODULES += lora
 PSEUDOMODULES += mpu_stack_guard
 PSEUDOMODULES += mpu_noexec_ram
+PSEUDOMODULES += mtd_write_page
 PSEUDOMODULES += nanocoap_%
 PSEUDOMODULES += netdev_default
 PSEUDOMODULES += netdev_ieee802154_%