> ## Documentation Index > Fetch the complete documentation index at: https://dragonwingdocs.qualcomm.com/llms.txt > Use this file to discover all available pages before exploring further. # Process the capsule The firmware on a device is updated using a capsule through UEFI. This process involves capturing the firmware update payload in a capsule \[.cap file], which is then processed by the system firmware to update the device firmware. The mentioned capsule update is applicable to Qualcomm Linux advanced and base variants only. ## **UEFI variables used in capsule update** Protocols and services that interact with the platform firmware enable communication between the OS and UEFI. UEFI offers a standard boot environment, data tables with platform information, and boot/runtime service calls for the OS loader and OS. | Variable name | Description | | --------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | **OsIndications** | This variable is owned by the OS and is used to indicate the features the OS wants the firmware to enable or the actions the OS wants the firmware to take. The operating system sets the variable, and UEFI clears it. | | **OsIndicationsSupported** | This variable is owned by the firmware and indicates which OS indication features and actions are supported by the firmware. | | **OsTrialBootStatus**
*(32‑bit UEFI variable)* | **Bit map:**

• **7:0 – Version**: Version number of `OsTrialBootStatus`
• **11:8 – TrialBootMaxCount**: Set by the OS before triggering the capsule update
• **15:12 – TrialBootCount**: Set or incremented by UEFI (if `TrialBootEnabled` is not cleared by OS). The OS may set this to `TrialBootMaxCount` to trigger firmware rollback
• **16 – TrialBootEnabled**: Set to `1` by UEFI after capsule update and cleared by the OS after successful OTA update
• **31:17 – Unused** | | **EFI system resource table (ESRT)** | The ESRT table is set by UEFI after the capsule update. | For more information about the OsIndications and OsIndicationsSupported variables, see [Exchanging information between the OS and Firmware](https://uefi.org/specs/UEFI/2.10/08_Services_Runtime_Services.html?highlight=osindications#exchanging-information-between-the-os-and-firmware). * If there is more than one capsule in the ESP partition (in EFI/UpdateCapsule), consider all the capsules for the update and update them alphabetically. * Store all UEFI non-volatile variables in the Rollback Protection Memory Block (RPMB) partition, which must be in a Provisioned state. * Autoprovision the RPMB on Qualcomm secure-boot enabled devices. * On Qualcomm non-secure devices, don’t autoprovision the RPMB; instead, provision it with test keys. * If you provision the RPMB with test keys on non-secure devices, you can’t re-provision it with a device key when enabling Qualcomm secure boot on the device. * Use the `rpmbClient` application for RPMB provisioning from Linux. For more information, see [Qualcomm Security Linux Guide](https://dragonwingdocs.qualcomm.com/System/Security/verify-the-security-configurations-of-qualcomm-linux). ## **EFI system resource table (ESRT) for capsule update status** The ESRT is an optional mechanism to identify the device and the system firmware resources that are used to provide firmware updates. Each ESRT entry describes a firmware resource that can be updated and reports the status of the last attempted update. The following table lists the ESRT entries used to report the status of the last attempted update: | **ESRT field** | **Description** | | ------------------------ | -------------------------------------------------------------------------------------------------------------------------------------- | | FwClass | Includes a GUID that identifies a firmware component for update through *UpdateCapsule().* | | FwType | Identifies the type of firmware resource. | | FwVersion | Represents the current version of the firmware resource. The value must always increase as a larger number represents a newer version. | | LowestSupportedFwVersion | Specifies the lowest firmware resource version to which the system or device can roll back to. | | CapsuleFlags | Contains the *CapsuleGuid* flags (bits 0-15) as defined in the *EFI\_CAPSULE\_HEADER* that’s set in the capsule header. | | LastAttemptVersion | Indicates the last firmware version for which the system attempted an update (uses the same format as the firmware version). | | LastAttemptStatus | Describes the result of the last firmware update attempt for the firmware resource entry. | The OS exposes the ESRT content from the sysfs path. ```text theme={null} /sys/firmware/efi/esrt/entries/entry0/ sh-5.1# cd /sys/firmware/efi/esrt/entries/entry0/ sh-5.1# ls capsule_flags fw_type last_attempt_status lowest_supported_fw_version w_class fw_version last_attempt_version ``` UEFI sets the ESRT table after the capsule update. X represents the firmware version before the capsule update. Y is the version of the firmware, which is available in the capsule \[.cap] file. Last attempted firmware version is available only if RPMB is provisioned. | **Last attempted firmware version** | **Current firmware version** | **last\_attempt\_status** | **Capsule update scenario** | | ----------------------------------- | ---------------------------- | ------------------------- | --------------------------- | | Y | Y | 0 | Update success | | Y | X | 1 | Capsule update failure | | 0 | X | 0 | Capsule meta-data failure | | Y | X | 0 | Firmware rollback done | For more information about ESRT, see [Firmware Update and Reporting - UEFI Specification 2.10 documentation](https://uefi.org/specs/UEFI/2.10/23_Firmware_Update_and_Reporting.html#efi-system-resource-table). ## **Firmware update using Capsule** The flowchart shows how to update the device firmware using the UEFI capsule method, leveraging different UEFI variables and supporting rollback.
Capsule flowchart
1. **Initiation**: The over the air (OTA) update process starts, and the OS prepares to update the capsule, signaling the UEFI (through setting `OsIndications`) to begin the update. The OS sets a `TrialBootMaxCount` to track the number of trial boots allowed and then reboots the device. 2. **UEFI update**: Upon reboot, the system checks for `OsIndications`. If present, it performs the capsule update, updates the EFI system resource table (ESRT), clears `OsIndications`, and if `TrialBootMaxCount` is set, allows `TrialBootEnabled` and restarts the system again. 3. **Trial boot handling**: * If the `OsIndications` aren’t set, the system checks if the `TrialBootEnabled` is active. * If the `TrialBootEnabled` is active and the `TrialBootCount` equals the `TrialBootMaxCount`, it checks the rollback count. * If a rollback is allowed, the UEFI reverts to the firmware, updates the ESRT, and reboots. * If a rollback isn’t allowed, it indicates that the rollback limit is reached. * If the `TrialBootCount` is less than the `TrialBootMaxCount`, it increments the `TrialBootCount` and continues the process. 4. **Completion**: The system boots to the OS, checks the ESRT, and if the OS boots successfully, it resets the `TrialBootEnabled` field. 5. **Result**: * If `TrialBootEnabled` isn’t active, the OTA update is confirmed as complete. * The system clears the `OtaTrialBootStatus` and sets the `LwSupportedFwVersion` to the current firmware version to disable rollback. 6. **Recovery**: If a firmware capsule update fails during the update process, UEFI has a recovery mechanism to maintain the stability and functionality. 1. **Rollback**: If rollback is allowed, UEFI reverts to the previous firmware version and restores the firmware to its state before the update attempt. 2. **ESRT update**: The system updates the ESRT to reflect the rollback. 3. **Reboot**: After the rollback is complete, the UEFI triggers a restart to ensure it’s running the previous, stable firmware version. This process applies the update and enables rollback if issues occur during the trial period. Authentication is critical to maintain security and stability during firmware updates. It helps with the following: * Ensures the system applies only updates from trusted sources. * Prevents malicious or unauthorized updates. * Verifies the digital signature to confirm integrity during transmission. * Installs only verified and tested updates. * Reduces the risk of system crashes or malfunctions caused by faulty firmware.