Unable to read from Flash using flash_area API even though the bytes are present

[Sameer Srivastava]

I have the following pm_static.yml configuration:

custom_bootloader:
  address: 0x0
  end_address: 0xc000
  placement:
    before:
    - tfm
  region: flash_primary
  size: 0xc000
custom_bootloader_header:
  address: 0xc000
  end_address: 0xc200
  placement:
    before:
    - tfm
  region: flash_primary
  size: 0x200
mcuboot_primary:
  address: 0xc000
  end_address: 0xf2000
  region: flash_primary
  orig_span: &id006
  - tfm
  - tfm_nonsecure
  size: 0xE6000
  span: *id006

and I'm trying to acces this `custom_bootloader_header` from my application code. Here's the relevant snippet:

#include <zephyr/storage/flash_map.h>
#include <flash_map_pm.h>



... {

        const struct flash_area *fa;
        printk("custom_bootloader_header: start=%ul, size=%ul\n", fa->fa_off, fa->fa_size);
        flash_area_open(header_flash_area_id, &fa);
        rc = flash_area_read(fa, 0, tags, 256);
        flash_area_close(fa);
}

prj.conf:

CONFIG_FLASH=y
CONFIG_NVS=y

The read function returns `-22`. I can't really do anything with the devicetree because those partitions are ignored when using a static configuration. Not sure what's going on.

[AHaug]

Hi,

The error indicates that the arguments are invalid, i.e https://docs.nordicsemi.com/bundle/zephyr-apis-latest/page/group_system_errno.html#ga2d1678d5a7cc8ce499643f3b8957def4 

From int flash_area_open ( uint8_t id, const struct flash_area ** fa ) I assume it's triggered by the first id argument. From https://github.com/nrfconnect/sdk-zephyr/blob/main/tests/subsys/fs/nvs/src/main.c you can see how you can set it up, i.e L:45 shows "err = flash_area_open(TEST_NVS_FLASH_AREA_ID, &fa);", and L:20 "#define TEST_NVS_FLASH_AREA_ID FIXED_PARTITION_ID(TEST_NVS_FLASH_AREA)" where TEST_NVS_FLASH_AREA is the storage_partition 

Could you state how you declare your "header_flash_area_id"? Is it only in the pm_static.yml? If so, how does the application become aware of this partition existing?

Another sample you can have a look at is the dfu_target.c from the mesh dfu target sample: https://github.com/nrfconnect/sdk-nrf/blob/4d3956f22283e35721c29eabb8093e493dce5456/samples/bluetooth/mesh/dfu/common/src/dfu_target.c#L47C8-L47C23 

Kind regards,
Andreas

[Sameer Srivastava]

Hi Andreas,

Thanks for the quick reply.

I use FIXED_PARTITION_ID(<label>) to get the id:

  int header_flash_area_id = FIXED_PARTITION_ID(custom_bootloader_header);

I make my application aware of the YML file in my top-level CMakeLists.txt:

set(PM_STATIC_YML_FILE ${CMAKE_CURRENT_SOURCE_DIR}/mcuboot/pm_static_nrf5340_dk_ns.yml)

Kind Regards,

Sameer