Hi Michal, On Fri, Dec 11, 2015 at 4:34 PM, Michal Suchanek <hramrach@xxxxxxxxx> wrote: > On 11 December 2015 at 09:44, Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote: >> On Thu, Dec 10, 2015 at 9:54 PM, Brian Norris >> <computersforpeace@xxxxxxxxx> wrote: >>> On Sat, Dec 05, 2015 at 11:15:54AM +0100, Geert Uytterhoeven wrote: >>>> On Sat, Dec 5, 2015 at 6:19 AM, Brian Norris >>>> <computersforpeace@xxxxxxxxx> wrote: >>>> > There have been several discussions [1] about adding a device tree binding for >>>> > associating flash devices with the partition parser(s) that are used on the >>>> > flash. There are a few reasons: >>>> > >>>> > (1) drivers shouldn't have to be encoding platform knowledge by listing what >>>> > parsers might be used on a given system (this is the currently all that's >>>> > supported) >>>> > (2) we can't just scan for all supported parsers (like the block system does), since >>>> > there is a wide diversity of "formats" (no standardization), and it is not >>>> > always safe or efficient to attempt to do so, particularly since many of >>>> > them allow their data structures to be placed anywhere on the flash, and >>>> > so require scanning the entire flash device to find them. >>>> >>>> I read the second reason, but would it be useful to (partially) merge >>>> block/partitions/ and drivers/mtd/partitions/, so I can use e.g. msdos >>>> partitions >>>> on an mtd device?? >>> >>> I kinda agree with Michal: is there a good use case? >> >> I don't have an immediate use case. >> Just looking at it from a high-level viewpoint. >> >>> Really, MTD partitioning is not a highly-scalable design. Particularly, >>> it's not typically that well-suited to large (read: unreliable) NAND >>> flash, where fixing partitions at the raw flash level mostly serves to >>> restrict UBI's ability to wear-level across the device. For that sort of >>> case, it's best if people are using UBI volumes on a (mostly?) >>> unpartitioned MTD, instead of using MTD partitions as the main >>> separation mechanism. Also, most partition designs (either MTD or block) >>> aren't very robust against bitflips, read disturb, etc. >>> >>> IOW, I wouldn't expect MBR or GPT to work well on large raw NAND flash, >>> and so I don't plan to do that sort of work myself. If you can provide >>> some better argument for it, and some nice maintainable code to go with >>> it, then of course it could be considered :) >> >> There's also NOR FLASH (e.g. SPI-NOR), which is what most boards I'm >> working on have. >> > > Yes, you can dump the content of a NOR flash to a file, attach a loop > device to it, and if block devices had the ability to use flash > partitioning access the different partitions. > > Maybe it would be more useful to use some kind of mtdloop, though. > There might even be one already. I never needed it. That's the inverse, which looks like a solid use case to me ;-) E.g. for investigation or virtualization. You can do this already in userspace with kpartx, though. Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html