nvmem: Add flash support

Allow flash devices to be accessed using the NVMEM API. Note that it simply
uses the read/write API functions. Erasing should be handled by the
application.

Signed-off-by: Pieter De Gendt <[email protected]>

Author: pdgendt

subsys/nvmem/Kconfig

@@ -11,6 +11,21 @@ config NVMEM_EEPROM
 	default y
 	depends on EEPROM
 
+config NVMEM_FLASH
+	bool "NVMEM (read) support for flash devices"
+	default y
+	depends on FLASH
+
+config NVMEM_FLASH_WRITE
+	bool "NVMEM write support for flash devices"
+	depends on NVMEM_FLASH
+	help
+	  Allow writing to NVMEM cells in flash devices.
+
+	  An explicit option is added for this as it's non-trivial
+	  to write to flash devices requiring out-of-bands erase or
+	  taking write-block sizes into account.
+
 module = NVMEM
 module-str = nvmem
 source "subsys/logging/Kconfig.template.log_config"

subsys/nvmem/nvmem.c

@@ -6,6 +6,7 @@
 
 #include <errno.h>
 #include <zephyr/drivers/eeprom.h>
+#include <zephyr/drivers/flash.h>
 #include <zephyr/nvmem.h>
 #include <zephyr/sys/__assert.h>
 
@@ -21,6 +22,10 @@ int nvmem_cell_read(const struct nvmem_cell *cell, void *buf, off_t off, size_t
 		return eeprom_read(cell->dev, cell->offset + off, buf, len);
 	}
 
+	if (IS_ENABLED(CONFIG_NVMEM_FLASH) && DEVICE_API_IS(flash, cell->dev)) {
+		return flash_read(cell->dev, cell->offset + off, buf, len);
+	}
+
 	return -ENXIO;
 }
 
@@ -40,5 +45,9 @@ int nvmem_cell_write(const struct nvmem_cell *cell, const void *buf, off_t off,
 		return eeprom_write(cell->dev, cell->offset + off, buf, len);
 	}
 
+	if (IS_ENABLED(CONFIG_NVMEM_FLASH_WRITE) && DEVICE_API_IS(flash, cell->dev)) {
+		return flash_write(cell->dev, cell->offset + off, buf, len);
+	}
+
 	return -ENXIO;
 }