mtd: Kconfig: add a Kconfig option to enable the support for MTD block write operations

This allows using CONFIG_IS_ENABLED(SPLMTD_WRITE) to compile out code
needed only if write support is required.
The option is added for u-boot and for SPL.

Signed-off-by: Jason Zhu <jason.zhu@rock-chips.com>
Change-Id: Ia48169fcd601ad51d1723923ed71d610901275e1

common/spl/Kconfig

@@ -482,6 +482,13 @@ config MTD_BLK_U_BOOT_OFFS
 	  Set the offset from the start of the nand,spi nand and nor flash where
 	  u-boot should be loaded from.
 
+config SPL_MTD_WRITE
+	bool "nand & spi nand & spi nor support for write operations in SPL"
+	depends on SPL_MTD_SUPPORT
+	default n
+	help
+	  Enable write access to nand & spi nand & spi nor in SPL
+
 config SPL_MUSB_NEW_SUPPORT
 	bool "Support new Mentor Graphics USB"
 	help

drivers/mtd/Kconfig

@@ -17,6 +17,13 @@ config MTD_BLK
 	help
 	  Enable mtd block model for Memory Technology Devices (MTD).
 
+config MTD_WRITE
+	bool "support for nand & spi nand & spi nor write operations"
+	depends on MTD_BLK
+	default y
+	help
+	  Enable write access to nand & spi nand & spi nor
+
 config MTD_NOR_FLASH
 	bool "Enable parallel NOR flash support"
 	help

drivers/mtd/mtd_blk.c

@@ -486,6 +486,7 @@ ulong mtd_dread(struct udevice *udev, lbaint_t start,
 	}
 }
 
+#if CONFIG_IS_ENABLED(MTD_WRITE)
 ulong mtd_dwrite(struct udevice *udev, lbaint_t start,
 		 lbaint_t blkcnt, const void *src)
 {
@@ -598,6 +599,7 @@ ulong mtd_derase(struct udevice *udev, lbaint_t start,
 
 	return 0;
 }
+#endif
 
 static int mtd_blk_probe(struct udevice *udev)
 {
@@ -648,8 +650,8 @@ static int mtd_blk_probe(struct udevice *udev)
 
 static const struct blk_ops mtd_blk_ops = {
 	.read	= mtd_dread,
+#if CONFIG_IS_ENABLED(MTD_WRITE)
 	.write	= mtd_dwrite,
-#ifndef CONFIG_SPL_BUILD
 	.erase	= mtd_derase,
 #endif
 };