mtd: nand: add a shorthand to generate nand_ecc_caps structure

struct nand_ecc_caps was designed as flexible as possible to support
multiple stepsizes (like sunxi_nand.c).

So, we need to write multiple arrays even for the simplest case.
I guess many controllers support a single stepsize, so here is a
shorthand macro for the case.

It allows to describe like ...

NAND_ECC_CAPS_SINGLE(denali_pci_ecc_caps, denali_calc_ecc_bytes, 512, 8, 15);

... instead of

static const int denali_pci_ecc_strengths[] = {8, 15};
static const struct nand_ecc_step_info denali_pci_ecc_stepinfo = {
        .stepsize = 512,
        .strengths = denali_pci_ecc_strengths,
        .nstrengths = ARRAY_SIZE(denali_pci_ecc_strengths),
};
static const struct nand_ecc_caps denali_pci_ecc_caps = {
        .stepinfos = &denali_pci_ecc_stepinfo,
        .nstepinfos = 1,
        .calc_ecc_bytes = denali_calc_ecc_bytes,
};
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>

include/linux/mtd/nand.h

@@ -505,6 +505,20 @@ struct nand_ecc_caps {
 	int (*calc_ecc_bytes)(int step_size, int strength);
 };
 
+/* a shorthand to generate struct nand_ecc_caps with only one ECC stepsize */
+#define NAND_ECC_CAPS_SINGLE(__name, __calc, __step, ...)	\
+static const int __name##_strengths[] = { __VA_ARGS__ };	\
+static const struct nand_ecc_step_info __name##_stepinfo = {	\
+	.stepsize = __step,					\
+	.strengths = __name##_strengths,			\
+	.nstrengths = ARRAY_SIZE(__name##_strengths),		\
+};								\
+static const struct nand_ecc_caps __name = {			\
+	.stepinfos = &__name##_stepinfo,			\
+	.nstepinfos = 1,					\
+	.calc_ecc_bytes = __calc,				\
+}
+
 /**
  * struct nand_ecc_ctrl - Control structure for ECC
  * @mode:	ECC mode