iio: core: Introduce IIO_VAL_INT_64.

Introduce IIO_VAL_INT_64 to read 64-bit value for
channel attribute. Val is used as lower 32 bits.
Signed-off-by: Andriy Tryshnivskyy <andriy.tryshnivskyy@opensynergy.com>
Link: https://lore.kernel.org/r/20211024091627.28031-2-andriy.tryshnivskyy@opensynergy.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/industrialio-core.c

@@ -702,6 +702,9 @@ static ssize_t __iio_format_value(char *buf, size_t offset, unsigned int type,
 	}
 	case IIO_VAL_CHAR:
 		return sysfs_emit_at(buf, offset, "%c", (char)vals[0]);
+	case IIO_VAL_INT_64:
+		tmp2 = (s64)((((u64)vals[1]) << 32) | (u32)vals[0]);
+		return sysfs_emit_at(buf, offset, "%lld", tmp2);
 	default:
 		return 0;
 	}

include/linux/iio/types.h

@@ -24,6 +24,7 @@ enum iio_event_info {
 #define IIO_VAL_INT_PLUS_NANO 3
 #define IIO_VAL_INT_PLUS_MICRO_DB 4
 #define IIO_VAL_INT_MULTIPLE 5
+#define IIO_VAL_INT_64 6 /* 64-bit data, val is lower 32 bits */
 #define IIO_VAL_FRACTIONAL 10
 #define IIO_VAL_FRACTIONAL_LOG2 11
 #define IIO_VAL_CHAR 12