unix: add GPIO constants and structs

This adds everything needed to use Linux's GPIO V2 UAPI, including the
ioctls, structs and constants.
As on some architectures char is signed by default and the UAPI doesn't
make it unsigned explicitly a mkpost fixup is used to make the types
more usable (by things like unix.ByteSliceToString).

Change-Id: Icdb0ca4a225316ca5e948e21ab21789636297a57
Reviewed-on: https://go-review.googlesource.com/c/sys/+/752623
Reviewed-by: David Chase <drchase@google.com>
Auto-Submit: Tobias Klauser <tobias.klauser@gmail.com>
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>

Author: lorenz

unix/linux/types.go

@@ -117,6 +117,7 @@ struct termios2 {
 #include <linux/fs.h>
 #include <linux/fsverity.h>
 #include <linux/genetlink.h>
+#include <linux/gpio.h>
 #include <linux/hdreg.h>
 #include <linux/hidraw.h>
 #include <linux/icmp.h>
@@ -6297,3 +6298,34 @@ const (
 	MPOL_PREFERRED_MANY      = C.MPOL_PREFERRED_MANY
 	MPOL_WEIGHTED_INTERLEAVE = C.MPOL_WEIGHTED_INTERLEAVE
 )
+
+// GPIO API
+const (
+	GPIO_GET_CHIPINFO_IOCTL          = C.GPIO_GET_CHIPINFO_IOCTL
+	GPIO_V2_GET_LINEINFO_IOCTL       = C.GPIO_V2_GET_LINEINFO_IOCTL
+	GPIO_V2_GET_LINE_IOCTL           = C.GPIO_V2_GET_LINE_IOCTL
+	GPIO_V2_LINE_GET_VALUES_IOCTL    = C.GPIO_V2_LINE_GET_VALUES_IOCTL
+	GPIO_V2_LINE_SET_VALUES_IOCTL    = C.GPIO_V2_LINE_SET_VALUES_IOCTL
+	GPIO_V2_GET_LINEINFO_WATCH_IOCTL = C.GPIO_V2_GET_LINEINFO_WATCH_IOCTL
+	GPIO_GET_LINEINFO_UNWATCH_IOCTL  = C.GPIO_GET_LINEINFO_UNWATCH_IOCTL
+)
+const (
+	GPIO_V2_LINE_ATTR_ID_FLAGS         = C.GPIO_V2_LINE_ATTR_ID_FLAGS
+	GPIO_V2_LINE_ATTR_ID_OUTPUT_VALUES = C.GPIO_V2_LINE_ATTR_ID_OUTPUT_VALUES
+	GPIO_V2_LINE_ATTR_ID_DEBOUNCE      = C.GPIO_V2_LINE_ATTR_ID_DEBOUNCE
+	GPIO_V2_LINE_CHANGED_REQUESTED     = C.GPIO_V2_LINE_CHANGED_REQUESTED
+	GPIO_V2_LINE_CHANGED_RELEASED      = C.GPIO_V2_LINE_CHANGED_RELEASED
+	GPIO_V2_LINE_CHANGED_CONFIG        = C.GPIO_V2_LINE_CHANGED_CONFIG
+	GPIO_V2_LINE_EVENT_RISING_EDGE     = C.GPIO_V2_LINE_EVENT_RISING_EDGE
+	GPIO_V2_LINE_EVENT_FALLING_EDGE    = C.GPIO_V2_LINE_EVENT_FALLING_EDGE
+)
+
+type GPIOChipInfo C.struct_gpiochip_info
+type GPIOV2LineValues C.struct_gpio_v2_line_values
+type GPIOV2LineAttribute C.struct_gpio_v2_line_attribute
+type GPIOV2LineConfigAttribute C.struct_gpio_v2_line_config_attribute
+type GPIOV2LineConfig C.struct_gpio_v2_line_config
+type GPIOV2LineRequest C.struct_gpio_v2_line_request
+type GPIOV2LineInfo C.struct_gpio_v2_line_info
+type GPIOV2LineInfoChanged C.struct_gpio_v2_line_info_changed
+type GPIOV2LineEvent C.struct_gpio_v2_line_event

unix/mkpost.go

@@ -194,6 +194,15 @@ func main() {
 		b = bytes.Replace(b, s, newNames, 1)
 	}
 
+	// Convert []int8 to []byte in GPIO structs
+	convertGPIONames := regexp.MustCompile(`(Name|Label|Consumer)(\s+)\[(\d+)\]u?int8`)
+	gpioTypes := regexp.MustCompile(`type GPIO\S+ struct {[^}]*}`)
+	gpioStructs := gpioTypes.FindAll(b, -1)
+	for _, s := range gpioStructs {
+		newNames := convertGPIONames.ReplaceAll(s, []byte("$1$2[$3]byte"))
+		b = bytes.Replace(b, s, newNames, 1)
+	}
+
 	// Convert []int8 to []byte in ctl_info ioctl interface
 	convertCtlInfoName := regexp.MustCompile(`(Name)(\s+)\[(\d+)\]int8`)
 	ctlInfoType := regexp.MustCompile(`type CtlInfo struct {[^}]*}`)