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Diffstat (limited to 'Documentation/driver-api/firmware')
5 files changed, 178 insertions, 0 deletions
diff --git a/Documentation/driver-api/firmware/core.rst b/Documentation/driver-api/firmware/core.rst index 1d1688cbc078..803cd574bbd7 100644 --- a/Documentation/driver-api/firmware/core.rst +++ b/Documentation/driver-api/firmware/core.rst @@ -13,4 +13,5 @@ documents these features. direct-fs-lookup fallback-mechanisms lookup-order + firmware-usage-guidelines diff --git a/Documentation/driver-api/firmware/firmware-usage-guidelines.rst b/Documentation/driver-api/firmware/firmware-usage-guidelines.rst new file mode 100644 index 000000000000..fdcfce42c6d2 --- /dev/null +++ b/Documentation/driver-api/firmware/firmware-usage-guidelines.rst @@ -0,0 +1,44 @@ +=================== +Firmware Guidelines +=================== + +Users switching to a newer kernel should *not* have to install newer +firmware files to keep their hardware working. At the same time updated +firmware files must not cause any regressions for users of older kernel +releases. + +Drivers that use firmware from linux-firmware should follow the rules in +this guide. (Where there is limited control of the firmware, +i.e. company doesn't support Linux, firmwares sourced from misc places, +then of course these rules will not apply strictly.) + +* Firmware files shall be designed in a way that it allows checking for + firmware ABI version changes. It is recommended that firmware files be + versioned with at least a major/minor version. It is suggested that + the firmware files in linux-firmware be named with some device + specific name, and just the major version. The firmware version should + be stored in the firmware header, or as an exception, as part of the + firmware file name, in order to let the driver detact any non-ABI + fixes/changes. The firmware files in linux-firmware should be + overwritten with the newest compatible major version. Newer major + version firmware shall remain compatible with all kernels that load + that major number. + +* If the kernel support for the hardware is normally inactive, or the + hardware isn't available for public consumption, this can + be ignored, until the first kernel release that enables that hardware. + This means no major version bumps without the kernel retaining + backwards compatibility for the older major versions. Minor version + bumps should not introduce new features that newer kernels depend on + non-optionally. + +* If a security fix needs lockstep firmware and kernel fixes in order to + be successful, then all supported major versions in the linux-firmware + repo that are required by currently supported stable/LTS kernels, + should be updated with the security fix. The kernel patches should + detect if the firmware is new enough to declare if the security issue + is fixed. All communications around security fixes should point at + both the firmware and kernel fixes. If a security fix requires + deprecating old major versions, then this should only be done as a + last option, and be stated clearly in all communications. + diff --git a/Documentation/driver-api/firmware/fw_upload.rst b/Documentation/driver-api/firmware/fw_upload.rst new file mode 100644 index 000000000000..76922591e446 --- /dev/null +++ b/Documentation/driver-api/firmware/fw_upload.rst @@ -0,0 +1,126 @@ +.. SPDX-License-Identifier: GPL-2.0 + +=================== +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(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 +------------------------ +.. kernel-doc:: drivers/base/firmware_loader/sysfs_upload.c + :identifiers: firmware_upload_register + +firmware_upload_unregister +-------------------------- +.. kernel-doc:: drivers/base/firmware_loader/sysfs_upload.c + :identifiers: firmware_upload_unregister + +Firmware Upload Ops +------------------- +.. kernel-doc:: include/linux/firmware.h + :identifiers: fw_upload_ops + +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. + +.. kernel-doc:: drivers/base/firmware_loader/sysfs_upload.h + :identifiers: fw_upload_prog + +Firmware Upload Error Codes +--------------------------- +The following error codes may be returned by the driver ops in case of +failure: + +.. kernel-doc:: include/linux/firmware.h + :identifiers: fw_upload_err + +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 diff --git a/Documentation/driver-api/firmware/index.rst b/Documentation/driver-api/firmware/index.rst index 57415d657173..9d2c19dc8e36 100644 --- a/Documentation/driver-api/firmware/index.rst +++ b/Documentation/driver-api/firmware/index.rst @@ -8,6 +8,7 @@ Linux Firmware API core efi/index request_firmware + fw_upload other_interfaces .. only:: subproject and html diff --git a/Documentation/driver-api/firmware/other_interfaces.rst b/Documentation/driver-api/firmware/other_interfaces.rst index b81794e0cfbb..06ac89adaafb 100644 --- a/Documentation/driver-api/firmware/other_interfaces.rst +++ b/Documentation/driver-api/firmware/other_interfaces.rst @@ -13,6 +13,12 @@ EDD Interfaces .. kernel-doc:: drivers/firmware/edd.c :internal: +Generic System Framebuffers Interface +------------------------------------- + +.. kernel-doc:: drivers/firmware/sysfb.c + :export: + Intel Stratix10 SoC Service Layer --------------------------------- Some features of the Intel Stratix10 SoC require a level of privilege |