FPGA Manager


The FPGA manager core exports a set of functions for programming an FPGA with an image. The API is manufacturer agnostic. All manufacturer specifics are hidden away in a low level driver which registers a set of ops with the core. The FPGA image data itself is very manufacturer specific, but for our purposes it’s just binary data. The FPGA manager core won’t parse it.

The FPGA image to be programmed can be in a scatter gather list, a single contiguous buffer, or a firmware file. Because allocating contiguous kernel memory for the buffer should be avoided, users are encouraged to use a scatter gather list instead if possible.

The particulars for programming the image are presented in a structure (struct fpga_image_info). This struct contains parameters such as pointers to the FPGA image as well as image-specific particulars such as whether the image was built for full or partial reconfiguration.

How to support a new FPGA device

To add another FPGA manager, write a driver that implements a set of ops. The probe function calls fpga_mgr_register(), such as:

static const struct fpga_manager_ops socfpga_fpga_ops = {
        .write_init = socfpga_fpga_ops_configure_init,
        .write = socfpga_fpga_ops_configure_write,
        .write_complete = socfpga_fpga_ops_configure_complete,
        .state = socfpga_fpga_ops_state,

static int socfpga_fpga_probe(struct platform_device *pdev)
        struct device *dev = &pdev->dev;
        struct socfpga_fpga_priv *priv;
        struct fpga_manager *mgr;
        int ret;

        priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
        if (!priv)
                return -ENOMEM;

         * do ioremaps, get interrupts, etc. and save
         * them in priv

        mgr = devm_fpga_mgr_create(dev, "Altera SOCFPGA FPGA Manager",
                                   &socfpga_fpga_ops, priv);
        if (!mgr)
                return -ENOMEM;

        platform_set_drvdata(pdev, mgr);

        return fpga_mgr_register(mgr);

static int socfpga_fpga_remove(struct platform_device *pdev)
        struct fpga_manager *mgr = platform_get_drvdata(pdev);


        return 0;

The ops will implement whatever device specific register writes are needed to do the programming sequence for this particular FPGA. These ops return 0 for success or negative error codes otherwise.

The programming sequence is::
  1. .write_init

  2. .write or .write_sg (may be called once or multiple times)

  3. .write_complete

The .write_init function will prepare the FPGA to receive the image data. The buffer passed into .write_init will be at most .initial_header_size bytes long; if the whole bitstream is not immediately available then the core code will buffer up at least this much before starting.

The .write function writes a buffer to the FPGA. The buffer may be contain the whole FPGA image or may be a smaller chunk of an FPGA image. In the latter case, this function is called multiple times for successive chunks. This interface is suitable for drivers which use PIO.

The .write_sg version behaves the same as .write except the input is a sg_table scatter list. This interface is suitable for drivers which use DMA.

The .write_complete function is called after all the image has been written to put the FPGA into operating mode.

The ops include a .state function which will determine the state the FPGA is in and return a code of type enum fpga_mgr_states. It doesn’t result in a change in state.

API for implementing a new FPGA Manager driver

  • fpga_mgr_states — Values for fpga_manager->state.

  • struct fpga_manager — the FPGA manager struct

  • struct fpga_manager_ops — Low level FPGA manager driver ops

  • devm_fpga_mgr_create() — Allocate and init a manager struct

  • fpga_mgr_register() — Register an FPGA manager

  • fpga_mgr_unregister() — Unregister an FPGA manager

enum fpga_mgr_states

fpga framework states



can’t determine state


FPGA power is off


FPGA reports power is up


FPGA in reset state


firmware request in progress


firmware request failed


preparing FPGA for programming


Error during WRITE_INIT stage


writing image to FPGA


Error while writing FPGA


Doing post programming steps




FPGA is programmed and operating

struct fpga_manager

fpga manager structure


struct fpga_manager {
  const char *name;
  struct device dev;
  struct mutex ref_mutex;
  enum fpga_mgr_states state;
  struct fpga_compat_id *compat_id;
  const struct fpga_manager_ops *mops;
  void *priv;



name of low level fpga manager


fpga manager device


only allows one reference to fpga manager


state of fpga manager


FPGA manager id for compatibility check.


pointer to struct of fpga manager ops


low level driver private date

struct fpga_manager_ops

ops for low level fpga manager drivers


struct fpga_manager_ops {
  size_t initial_header_size;
  enum fpga_mgr_states (*state)(struct fpga_manager *mgr);
  u64 (*status)(struct fpga_manager *mgr);
  int (*write_init)(struct fpga_manager *mgr,struct fpga_image_info *info, const char *buf, size_t count);
  int (*write)(struct fpga_manager *mgr, const char *buf, size_t count);
  int (*write_sg)(struct fpga_manager *mgr, struct sg_table *sgt);
  int (*write_complete)(struct fpga_manager *mgr, struct fpga_image_info *info);
  void (*fpga_remove)(struct fpga_manager *mgr);
  const struct attribute_group **groups;



Maximum number of bytes that should be passed into write_init


returns an enum value of the FPGA’s state


returns status of the FPGA, including reconfiguration error code


prepare the FPGA to receive confuration data


write count bytes of configuration data to the FPGA


write the scatter list of configuration data to the FPGA


set FPGA to operating state after writing is done


optional: Set FPGA into a specific state during driver remove


optional attribute groups.


fpga_manager_ops are the low level functions implemented by a specific fpga manager driver. The optional ones are tested for NULL before being called, so leaving them out is fine.

struct fpga_manager *devm_fpga_mgr_create(struct device *dev, const char *name, const struct fpga_manager_ops *mops, void *priv)

create and initialize a managed FPGA manager struct


struct device * dev

fpga manager device from pdev

const char * name

fpga manager name

const struct fpga_manager_ops * mops

pointer to structure of fpga manager ops

void * priv

fpga manager private data


This function is intended for use in a FPGA manager driver’s probe function. After the manager driver creates the manager struct with devm_fpga_mgr_create(), it should register it with fpga_mgr_register(). The manager driver’s remove function should call fpga_mgr_unregister(). The manager struct allocated with this function will be freed automatically on driver detach. This includes the case of a probe function returning error before calling fpga_mgr_register(), the struct will still get cleaned up.


pointer to struct fpga_manager or NULL

int fpga_mgr_register(struct fpga_manager *mgr)

register a FPGA manager


struct fpga_manager * mgr

fpga manager struct


0 on success, negative error code otherwise.

void fpga_mgr_unregister(struct fpga_manager *mgr)

unregister a FPGA manager


struct fpga_manager * mgr

fpga manager struct


This function is intended for use in a FPGA manager driver’s remove function.