On Fri, Dec 15, 2023 at 5:17 PM Sebastien Lorquet <sebast...@lorquet.fr> wrote:
> Hi, > > I dont think you can use losetup to create a mtd device. loop devices > are regular block devices. You can use lomtd to setup a mtd device loop: https://github.com/apache/nuttx-apps/blob/master/nshlib/nsh_fscmds.c#L1144-L1306 > This will only work if littlefs can mount a > block device (no idea if thats possible) > > Yes, littlefs can work with block devices directly, the difference between mtd and block is hidden by littlefs wrapper. Of course, littlefs isn't an efficient solution for block devices since the wear leveling built inside littlefs is useless and harms the performance a lot. > what you need is an adaptation layer that will implement a mtd device on > an eeprom. > > You can duplicate a spi flash driver, and change its read/erase/write > routines (and initialization) by copying code from a spi eeprom driver. > > Sebastien. > > Le 14/12/2023 à 19:13, Tim Hardisty a écrit : > > Question first, then explanation. > > > > How do I use losetup (which is what I think I need) with a character > > memory device and mount an FS on it? SPI EEPROM and LittleFS > > specifically. > > > > Yes, it's a bad idea, probably, but I just want to have a play and > > lack of NuttX/POSIX/Linux knowledge has bitten my behind again. This > > is perhaps the 3rd time over the years I've asked but even checking > > the dev emails archive and I can't find what I need. > > > > SPI EEPROM is correctly registered as /dev/at25 and I can > > read/write/etc to it as a character device. NB: it does not initialize > > in the same way as an I2C EEPROM so you can't directly initialise it > > as an mtd. It is for storage of settings, and some of the values may > > change 10,000's time over the life of the product, hence EEPROM with > > 1,000,000+ write cycles. > > > > But there is then no wear levelling or anything like that as just a > > character device, so I thought I'd have a play, and LittleFS has a > > small minimum sector size and *might* work. A quick Google turns up > > the same Linux-related losetup examples that don't seem relevant; my > > Googling skills are probably as bad as those of my software > > engineering <grin><rolleyes>. > > > > Any pointers/suggestions please? > > >
