Am 19.03.2014 15:44, wrote Wolfgang Denk: > Dear Eric Nelson, > > In message <5329a80b.9020...@boundarydevices.com> you wrote: >> >>> short question to the usage of the mmc command (and also the mmc >>> driver API): is it intended that mmc read / write may fail when the >>> supplied address in RAM is not aligned? >> >> If not intended, it is known. > > I consider this a known bug. > >>> ARMV7 will give output like this: >>> >>> U-Boot > mmc read 12000002 44 44 >>> >> Why would you want to do this? > > For example, BMP images require loading on a +2 aligned address due to > their stupid header format. I ran into this before myself: it is > impossible to match both the alignment reuqirements of the bmp command > and the mmc read command at the same time. One must manually copy the > memory ragen again. This is a plain, stupid bug. >
Exactly here it popped up ... >>> Special commands inside the mmc drivers and in env_mmc implement the >>> alignment magic. Shouldn't the mmc do the magic (and if neccesarry >>> provide help using temp buffers if needed) so that all users outside can >>> read / write without caring for special cases? >> >> Is there a use case here? There are plenty of memory addresses that >> won't work with commands like "mmc read". > env_mmc needs to care for cache aligned buffers - This was fixed some time ago for the redundant env case > "mmc read" and "mmc write" are operations that work on character > buffers, like all other file IO ops. These should not require any > specific alignment. > >> Is it worth **any** code to try and catch them? > > Definitely yes. > So just as an idea - we could use a bounce buffer for mmc_bwrite / mmc_bread for the unaligned case. Is definitely slow but should work. > Best regards, > > Wolfgang Denk > _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
