Firmware Upload API¶

A device driver that registers with the firmware loader will expose persistent sysfs nodes to enable users to initiate firmware updates for that device. It is the responsibility of the device driver and/or the device itself to perform any validation on the data received. Firmware upload uses the same loading and data sysfs files described in the documentation for firmware fallback. It also adds additional sysfs files to provide status on the transfer of the firmware image to the device.

Register for firmware upload¶

A device driver registers for firmware upload by calling firmware_upload_register(). Among the parameter list is a name to identify the device under /sys/class/firmware. A user may initiate a firmware upload by echoing a 1 to the loading sysfs file for the target device. Next, the user writes the firmware image to the data sysfs file. After writing the firmware data, the user echos 0 to the loading sysfs file to signal completion. Echoing 0 to loading also triggers the transfer of the firmware to the lower-lever device driver in the context of a kernel worker thread.

To use the firmware upload API, write a driver that implements a set of ops. The probe function calls firmware_upload_register() and the remove function calls firmware_upload_unregister() such as:

static const struct fw_upload_ops m10bmc_ops = {
        .prepare = m10bmc_sec_prepare,
        .write = m10bmc_sec_write,
        .poll_complete = m10bmc_sec_poll_complete,
        .cancel = m10bmc_sec_cancel,
        .cleanup = m10bmc_sec_cleanup,
};

static int m10bmc_sec_probe(struct platform_device *pdev)
{
        const char *fw_name, *truncate;
        struct m10bmc_sec *sec;
        struct fw_upload *fwl;
        unsigned int len;

        sec = devm_kzalloc(&pdev->dev, sizeof(*sec), GFP_KERNEL);
        if (!sec)
                return -ENOMEM;

        sec->dev = &pdev->dev;
        sec->m10bmc = dev_get_drvdata(pdev->dev.parent);
        dev_set_drvdata(&pdev->dev, sec);

        fw_name = dev_name(sec->dev);
        truncate = strstr(fw_name, ".auto");
        len = (truncate) ? truncate - fw_name : strlen(fw_name);
        sec->fw_name = kmemdup_nul(fw_name, len, GFP_KERNEL);

        fwl = firmware_upload_register(THIS_MODULE, sec->dev, sec->fw_name,
                                       &m10bmc_ops, sec);
        if (IS_ERR(fwl)) {
                dev_err(sec->dev, "Firmware Upload driver failed to start\n");
                kfree(sec->fw_name);
                return PTR_ERR(fwl);
        }

        sec->fwl = fwl;
        return 0;
}

static int m10bmc_sec_remove(struct platform_device *pdev)
{
        struct m10bmc_sec *sec = dev_get_drvdata(&pdev->dev);

        firmware_upload_unregister(sec->fwl);
        kfree(sec->fw_name);
        return 0;
}

firmware_upload_register¶

struct fw_upload *firmware_upload_register(struct module *module, struct device *parent, const char *name, const struct fw_upload_ops *ops, void *dd_handle)¶: register for the firmware upload sysfs API

Parameters

struct module *module

kernel module of this device

struct device *parent

parent device instantiating firmware upload

const char *name

firmware name to be associated with this device

const struct fw_upload_ops *ops

pointer to structure of firmware upload ops

void *dd_handle

pointer to parent driver private data

name must be unique among all users of firmware upload. The firmware sysfs files for this device will be found at /sys/class/firmware/name.

Return

struct fw_upload pointer or ERR_PTR()

firmware_upload_unregister¶

void firmware_upload_unregister(struct fw_upload *fw_upload)¶: Unregister firmware upload interface

Parameters

struct fw_upload *fw_upload: pointer to struct fw_upload

Firmware Upload Ops¶

struct fw_upload_ops¶: device specific operations to support firmware upload

Definition:

struct fw_upload_ops {
    enum fw_upload_err (*prepare)(struct fw_upload *fw_upload, const u8 *data, u32 size);
    enum fw_upload_err (*write)(struct fw_upload *fw_upload,const u8 *data, u32 offset, u32 size, u32 *written);
    enum fw_upload_err (*poll_complete)(struct fw_upload *fw_upload);
    void (*cancel)(struct fw_upload *fw_upload);
    void (*cleanup)(struct fw_upload *fw_upload);
};

Members

prepare: Required: Prepare secure update
write: Required: The write() op receives the remaining size to be written and must return the actual size written or a negative error code. The write() op will be called repeatedly until all data is written.
poll_complete: Required: Check for the completion of the HW authentication/programming process.
cancel: Required: Request cancellation of update. This op is called from the context of a different kernel thread, so race conditions need to be considered.
cleanup: Optional: Complements the prepare() function and is called at the completion of the update, on success or failure, if the prepare function succeeded.

Firmware Upload Progress Codes¶

The following progress codes are used internally by the firmware loader. Corresponding strings are reported through the status sysfs node that is described below and are documented in the ABI documentation.

enum fw_upload_prog¶: firmware upload progress codes

Constants

FW_UPLOAD_PROG_IDLE: there is no firmware upload in progress
FW_UPLOAD_PROG_RECEIVING: worker thread is receiving firmware data
FW_UPLOAD_PROG_PREPARING: target device is preparing for firmware upload
FW_UPLOAD_PROG_TRANSFERRING: data is being copied to the device
FW_UPLOAD_PROG_PROGRAMMING: device is performing the firmware update
FW_UPLOAD_PROG_MAX: Maximum progress code marker

Firmware Upload Error Codes¶

The following error codes may be returned by the driver ops in case of failure:

enum fw_upload_err¶: firmware upload error codes

Constants

FW_UPLOAD_ERR_NONE: returned to indicate success
FW_UPLOAD_ERR_HW_ERROR: error signalled by hardware, see kernel log
FW_UPLOAD_ERR_TIMEOUT: SW timed out on handshake with HW/firmware
FW_UPLOAD_ERR_CANCELED: upload was cancelled by the user
FW_UPLOAD_ERR_BUSY: there is an upload operation already in progress
FW_UPLOAD_ERR_INVALID_SIZE: invalid firmware image size
FW_UPLOAD_ERR_RW_ERROR: read or write to HW failed, see kernel log
FW_UPLOAD_ERR_WEAROUT: FLASH device is approaching wear-out, wait & retry
FW_UPLOAD_ERR_MAX: Maximum error code marker

Sysfs Attributes¶

In addition to the loading and data sysfs files, there are additional sysfs files to monitor the status of the data transfer to the target device and to determine the final pass/fail status of the transfer. Depending on the device and the size of the firmware image, a firmware update could take milliseconds or minutes.

The additional sysfs files are:

status - provides an indication of the progress of a firmware update
error - provides error information for a failed firmware update
remaining_size - tracks the data transfer portion of an update
cancel - echo 1 to this file to cancel the update

The Linux Kernel

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