partition manager: how to define a region with multiple partitions and use it in application code.

Question

Maybe someone can help ... 
 Context: We are in the process of migrating a project from Stm32F to nrf5340 using Zephyr. Our firmware is functional (currently without a possibility to perform a firmware update over Bluetooth (using DFU). Now we want to add DeviceFirmwareUpdate, since this is a requirement. - we tested the SimpleMessageProtocol example, which includes the MCUBootloader, which works fine). We have update our code using the experience from above mentioned SMP example. The problem we now have is, that we want to define flash area for DATAStorage in our application and dont know how to add this to the memory map. 
 We dont' want to use the NVS (since the DATAStorage contains a huge block of 148kB of data which is optimized for memory storage). 
 - i read the partition_manager documentation. - I am stuck at the point where to define a new region? (since this seems to be done in nordicsemi\v2.0.0
rf\cmake\partition_manager.cmake). - can any one point me to an example or to a direction how to : - define the region and partition(s) for usage by the partition manager - access the defined region partition in code, so that we can read/write to it from within the application code Thanks in advance, René

Vidar Berg · Accepted Answer

Hi,

The PM should allocate a separate partition for littleFS if you add this to your board overlay:

/ {
	fstab {
		compatible = "zephyr,fstab";
		lfs1: lfs1 {
			compatible = "zephyr,fstab,littlefs";
			mount-point = "/lfs1";
			partition = <&storage_partition>;
			automount;
			read-size = <16>;
			prog-size = <16>;
			cache-size = <64>;
			lookahead-size = <32>;
			block-cycles = <512>;
		};
	};
};

You can then use the CONFIG_PM_PARTITION_SIZE_LITTLEFS symbol to adjust the size of the partition.

Best regards,

Vidar

reneTrumpet · Answer

Hi Flavio, 
 Thanks for your reply. 
 Maybe since i am new on this forum and don't know the rules, i forgot to mark the answer from VIDAR as answer to my question. But thank you for replying. 
 The solution from Vidar worked perfect for me and was very simple at the end. 
 When the fstab (file system table) is added to the devicetree (see above post from Vidar) , it automounts the littlefs. 
 Then i can write to file with the normal filesystem api (the important thing is that the filename includes the mountpoint name) . 
 Below a snippit of my code (i removed the error handling for readability), code is not tested! 
 the invocation will be: LITTLEFS_WriteFile("/lfs1/logdata", "dummydata", 9 ); 
 !!Note the "lfs1" before the filename, by use of the mountpoint the filesystem knows what mount to use and in this case uses the littlefs. 
 /**
 * @brief rewrite the data with size numBytes to the file specified by filename
 *
 * @param filename the filename (relative to mount root).
 * @param data the data to write
 * @param numBytes the number of Bytes to write to the file
 * @note file will always be overwritten, if file does not exist, it will be created.
 */
LITTLEFS_WriteFile(const uint8_t filename[],
 uint8_t data[],
 const uint32_t numBytes)
{
 struct fs_file_t file;
 int rc;
 
 /* initialize the file structure */
 fs_file_t_init(&file);

 /* always remove the current file: since a new file must be written */
 fs_unlink(filename);

 /* open the file*/
 rc = fs_open(&file, filename, FS_O_CREATE | FS_O_RDWR);
 if (rc >= 0)
 {
 /* overwrite the file with the new contents */
 rc = fs_write(&file, &data[0], numBytes);
 if (rc >= 0) {
 result = RESULT_ERROR_LFS_WRITE;
 }
 }

 /* always close the file (with exception of LFS_OPEN) */
 fs_close(&file);
}

partition manager: how to define a region with multiple partitions and use it in application code.

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