I will only be making a few 100 changes over the life of the product. It’s a
holding area for a new firmware image to be written via USBMSD by the user and
used by MCUboot to write out (raw) to the main boot flash. Ideally I would like
a “FAT translator” that allows (say) a LittleFS partition to be seen as FAT via
USB but I don’t think such a thing exists.
Obviously FAT is useless on flash for more “normal” things, which is why I have
a 32MByte NOR flash running LittleFS for syslog and userlogs. In the limit I
may just use a FAT formatted RAMdisk for the upgrade staging, but it depends on
how much RAM my app ends up needing.
> On 1 Nov 2024, at 15:12, Xiang Xiao <xiaoxiang781...@gmail.com> wrote:
>
> it mayn't work as you expect. FatFS updates some fixed location very
> frequently, your flash device may stop working after you make ten thousand
> changes.
>
> On Fri, Nov 1, 2024 at 8:06 PM Tim hardisty <timhardist...@gmail.com> wrote:
>
>> I am successfully creating a FAT FS on a QSPI NOR flash - the problem
>> was an error in the flash driver when 512 byte sector emulation was
>> being used. I do this in my bringup code:
>> struct qspi_dev_s *qspi_flashmem;
>>
>> qspi_flashmem = sam_qspi_initialize(0);
>> ...
>> mtd_qspi = gd55_initialize(qspi_flashmem, 0);
>> ...
>> mtd_qspi0 = mtd_partition(mtd_qspi, 0, QSPI0_SIZE);...
>> ...
>> ret = register_mtddriver("/dev/qspi0", mtd_qspi0, 0744, NULL);
>> ...
>> mtd_qspi1 = mtd_partition(mtd_qspi, QSPI0_SIZE, QSPI1_SIZE);
>> ...
>> ret = register_mtddriver("/dev/qspi1", mtd_qspi1, 0755, NULL);
>> ret = nx_mount("/dev/qspi1", "/mnt/qspi1lfs", "littlefs", 0, "autoformat");
>> etc.
>>
>> The GD55 driver is using 512 byte simulation, but s512_initialize()
>> works just as well.
>>
>> I can then use mkfatfs to create a FAT FS and mount it and all is good.
>>
>> mkfats fs is not available to use in bringup code as I understand it
>> otherwise I would mount the FS in my bringup too.
>>
>> On 01/11/2024 02:07, Xiang Xiao wrote:
>>> On Wed, Oct 30, 2024 at 2:00 AM Tim Hardisty <timhardist...@gmail.com>
>>> wrote:
>>>
>>>> Whilst FAT on a NOR flash may generally be seen a not such a great
>>>> idea...please ignore that and confirm if...
>>>>
>>>> ...I am right in deducing that I can't simply make a FAT file system on
>>>> (say) the third mtd partition (with 512 byte sector emulation)
>>>> (partitions 0, 1 and 2 are "raw" data) since FAT will treat the entire
>>>> flash devices as a "volume" and so fail to find a partition table at the
>>>> bottom end of the flash device?
>>>
>>> The partition is different from the file system. A file system can mount
>> on
>>> either a block/mtd device, or a partition. FAT can work only with the
>> block
>>> device, so you can't mount FAT on a flash(mtd) device, only the special
>>> designed file system(e.g. littlefs, smartfs, spiffs) can work with mtd
>>> device directly. The traditional block based file system need FTL(flash
>>> translation layer) to work with mtd device, so you can try dhara if you
>>> really want to use FAT on flash device:
>>> https://github.com/apache/nuttx/blob/master/drivers/mtd/dhara.c
>>>
>>> If so, it no doubt explains why I can
>>>> format a FAT FS but not mount it.
>>>>
>>>>
>>> Which command do you use to format the device or partition?
>>>
>>> I could - perhaps should - re-jig my partitions so partition 0 is used
>>>> for FAT, rather than partition 3, but before I do that are there any FAT
>>>> FA/NuttX gurus who can let me know if there is a way to do this (and
>>>> save me the hassle of reworking my bootstrap and MCUboot locations etc.
>>>> for now)?
>>>
>>> You can format the device with GPT/MBR partition by:
>>> https://github.com/apache/nuttx-apps/tree/master/fsutils/mkgpt
>>> https://github.com/apache/nuttx-apps/tree/master/fsutils/mkmbr
>>> But, the raw flash device normally doesn't use GPT/MBR partition, instead
>>> hardcode the partition in the code directly since CPU normally could run
>>> firmware directly on flash devices which normally define a proprietary
>>> partition scheme. For this case, you can use PTABLE/TXTABLE:
>>> https://github.com/apache/nuttx/blob/master/fs/partition/fs_ptable.c
>>> https://github.com/apache/nuttx/blob/master/fs/partition/fs_txtable.c
>>>
>>
