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-rw-r--r--Documentation/fpga/fpga-mgr.txt35
1 files changed, 26 insertions, 9 deletions
diff --git a/Documentation/fpga/fpga-mgr.txt b/Documentation/fpga/fpga-mgr.txt
index 6ebc714f4b03..cc6413ed6fc9 100644
--- a/Documentation/fpga/fpga-mgr.txt
+++ b/Documentation/fpga/fpga-mgr.txt
@@ -48,8 +48,20 @@ To get/put a reference to a FPGA manager:
struct fpga_manager *fpga_mgr_get(struct device *dev);
void fpga_mgr_put(struct fpga_manager *mgr);
-Given a DT node or device, get an exclusive reference to a FPGA manager.
-fpga_mgr_put releases the reference.
+Given a DT node or device, get a reference to a FPGA manager. This pointer
+can be saved until you are ready to program the FPGA. fpga_mgr_put releases
+the reference.
+
+
+To get exclusive control of a FPGA manager:
+-------------------------------------------
+
+ int fpga_mgr_lock(struct fpga_manager *mgr);
+ void fpga_mgr_unlock(struct fpga_manager *mgr);
+
+The user should call fpga_mgr_lock and verify that it returns 0 before
+attempting to program the FPGA. Likewise, the user should call
+fpga_mgr_unlock when done programming the FPGA.
To register or unregister the low level FPGA-specific driver:
@@ -67,13 +79,21 @@ device."
How to write an image buffer to a supported FPGA
================================================
-/* Include to get the API */
#include <linux/fpga/fpga-mgr.h>
struct fpga_manager *mgr;
struct fpga_image_info *info;
int ret;
+/*
+ * Get a reference to FPGA manager. The manager is not locked, so you can
+ * hold onto this reference without it preventing programming.
+ *
+ * This example uses the device node of the manager. Alternatively, use
+ * fpga_mgr_get(dev) instead if you have the device.
+ */
+mgr = of_fpga_mgr_get(mgr_node);
+
/* struct with information about the FPGA image to program. */
info = fpga_image_info_alloc(dev);
@@ -99,17 +119,14 @@ if (image is in a scatter gather table) {
}
-/*
- * Get a reference to FPGA manager. This example uses the device node of the
- * manager. You could use fpga_mgr_get() instead if you have the device instead
- * of the device node.
- */
-mgr = of_fpga_mgr_get(mgr_node);
+/* Get exclusive control of FPGA manager */
+ret = fpga_mgr_lock(mgr);
/* Load the buffer to the FPGA */
ret = fpga_mgr_buf_load(mgr, &info, buf, count);
/* Release the FPGA manager */
+fpga_mgr_unlock(mgr);
fpga_mgr_put(mgr);
/* Deallocate the image info if you're done with it */