Are there any test cases that could be used to verify the PR? It's a large change but I don't see any testing logs in the PR. I think this should be tested with a few different devices before getting merged, and the results recorded.
Matteo On Thu, Jul 10, 2025 at 1:25 PM Tomek CEDRO <to...@cedro.info> wrote: > Hello world :-) > > There is interesting update PR to bch / mtd / ftl / fs subsystems that > increased granularity of control and improved performance (write). > Please take a look, any hints are welcome especially from people using > them that may be affected or verify the improvement :-) > > The solution provides backward compatible behavior but the functions > API will be changed with new flags field added so build errors may pop > up after this change. > > https://github.com/apache/nuttx/pull/16642 > > Summary > > **To save more space (equivalent to the size of one erase sector of > MTD device) and to achieve faster read and write speeds, a method for > direct writing was introduced at the FTL layer. This can be > accomplished simply by using the following oflags during > the open operation: > > O_DIRECT. when this flag is passed in, ftl internally uses the > direct write strategy and no read cache is used in ftl; > otherwise, each write will be executed with the minimum > granularity of flash erase sector size which means a > "sector read back - erase sector - write sector" operation is > performed by using a read cache buffer in heap. > > O_SYNC. When this flag is passed in, we assume that the flash has > been erased in advance and no erase operation > will be performed internally within ftl. O_SYNC will take effect > only when both O_DIRECT and O_SYNC are passed in > simultaneously. > > For uniformity, we remapped the mount flag in mount.h and unified > it with the open flag in fcntl.h. The repetitive > parts of their definitions were reused, and the remaining part of > the mount flag redefine to the unused bit of open > flags.** > > Impact > > When an application wants to bypass the following logic in the FTL > layer during the process of writing to Flash: using the sector size as > the buffer for "read-back - erase - write", the MTD device node can be > opened with the O_DIRECT flag. At this point, the FTL will directly > write to the MTD device. The open method is as follows: > fd = open("/dev/mtd_device", O_RDWR | O_DIRECT); > > If the application ensures that the flash has been erased in advance, > then adding the O_SYNC logic can control the FTL not to perform > erasure. The open method is as follows: > fd = open("/dev/mtd_device", O_RDWR | O_DIRECT | O_SYNC); > > -- > CeDeROM, SQ7MHZ, http://www.tomek.cedro.info >
