On Mon, Dec 11, 2017 at 6:26 PM, Arnd Bergmann [off-list ref] wrote:

On Mon, Dec 11, 2017 at 6:06 AM, Joel Stanley [off-list ref] wrote:

quoted

These are used to by the device tree to map pin numbers to constants
required by the GPIO bindings.
+
+#define ASPEED_GPIO_PORT_A 0
+#define ASPEED_GPIO_PORT_B 1
+#define ASPEED_GPIO_PORT_C 2
+#define ASPEED_GPIO_PORT_D 3
+#define ASPEED_GPIO_PORT_E 4
+#define ASPEED_GPIO_PORT_F 5
+#define ASPEED_GPIO_PORT_G 6
+#define ASPEED_GPIO_PORT_H 7
+#define ASPEED_GPIO_PORT_I 8
+#define ASPEED_GPIO_PORT_J 9
+#define ASPEED_GPIO_PORT_K 10
+#define ASPEED_GPIO_PORT_L 11
+#define ASPEED_GPIO_PORT_M 12
+#define ASPEED_GPIO_PORT_N 13
+#define ASPEED_GPIO_PORT_O 14
+#define ASPEED_GPIO_PORT_P 15
+#define ASPEED_GPIO_PORT_Q 16
+#define ASPEED_GPIO_PORT_R 17
+#define ASPEED_GPIO_PORT_S 18
+#define ASPEED_GPIO_PORT_T 19
+#define ASPEED_GPIO_PORT_U 20
+#define ASPEED_GPIO_PORT_V 21
+#define ASPEED_GPIO_PORT_W 22
+#define ASPEED_GPIO_PORT_X 23
+#define ASPEED_GPIO_PORT_Y 24
+#define ASPEED_GPIO_PORT_Z 25
+#define ASPEED_GPIO_PORT_AA 26
+#define ASPEED_GPIO_PORT_AB 27
+#define ASPEED_GPIO_PORT_AC 28

This looks like a 1:1 mapping, wouldn't it be easier to just describe
it in the binding document?

You're right, it is a linear mapping. We use it so references to GPIO
numbers are human readable in the device tree:

#define ASPEED_GPIO(port, offset) \
        ((ASPEED_GPIO_PORT_##port * 8) + offset)

can be used:

                identify {
                        gpios = <&gpio ASPEED_GPIO(A, 2) GPIO_ACTIVE_LOW>;
                };

We find that has cut down on mistakes in calculating offsets into GPIO banks.

Cheers,

Joel