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
