Add option to disable MMAP API

Since the high-speed MMAP API is specific to Analog Devices' Linux
kernel, add an option to disable it.

Signed-off-by: Paul Cercueil <[email protected]>

Author: pcercuei

CMakeLists.txt

@@ -247,6 +247,7 @@ if(WITH_LOCAL_BACKEND)
 		list(APPEND LIBIIO_CFILES ./libini/libini.c)
 	endif()
 
+	option(WITH_LOCAL_MMAP_API "Use the mmap API provided in Analog Devices' kernel (not upstream)" ON)
 	option(WITH_HWMON "Add compatibility with the hardware monitoring (hwmon) subsystem" OFF)
 endif()
 
@@ -621,6 +622,7 @@ list(APPEND IIO_FEATURES_${HAVE_BONJOUR} bonjour)
 list(APPEND IIO_FEATURES_${ENABLE_IPV6} ipv6)
 list(APPEND IIO_FEATURES_${WITH_SERIAL_BACKEND} serial)
 list(APPEND IIO_FEATURES_${WITH_LOCAL_BACKEND} local)
+list(APPEND IIO_FEATURES_${WITH_LOCAL_MMAP_API} local-mmap)
 list(APPEND IIO_FEATURES_${WITH_HWMON} hwmon)
 list(APPEND IIO_FEATURES_${WITH_USB_BACKEND} usb)
 list(APPEND IIO_FEATURES_${WITH_TESTS} utils)

iio-config.h.cmakein

@@ -18,6 +18,7 @@
 #cmakedefine01 WITH_IIOD_USBD
 #cmakedefine01 WITH_IIOD_SERIAL
 #cmakedefine01 WITH_LOCAL_CONFIG
+#cmakedefine01 WITH_LOCAL_MMAP_API
 #cmakedefine01 WITH_HWMON
 #cmakedefine01 WITH_AIO
 #cmakedefine01 HAVE_DNS_SD

local.c

@@ -439,7 +439,7 @@ static ssize_t local_get_buffer(const struct iio_device *dev,
 	int f = pdata->fd;
 	ssize_t ret;
 
-	if (!pdata->is_high_speed)
+	if (!WITH_LOCAL_MMAP_API || !pdata->is_high_speed)
 		return -ENOSYS;
 	if (f == -1)
 		return -EBADF;
@@ -957,11 +957,13 @@ static int local_open(const struct iio_device *dev,
 	pdata->cyclic_buffer_enqueued = false;
 	pdata->samples_count = samples_count;
 
-	ret = enable_high_speed(dev);
-	if (ret < 0 && ret != -ENOSYS)
-		goto err_close;
+	if (WITH_LOCAL_MMAP_API) {
+		ret = enable_high_speed(dev);
+		if (ret < 0 && ret != -ENOSYS)
+			goto err_close;
 
-	pdata->is_high_speed = !ret;
+		pdata->is_high_speed = !ret;
+	}
 
 	if (!pdata->is_high_speed) {
 		unsigned long size = samples_count * pdata->max_nb_blocks;