On Monday, August 29, 2011 21:49:33 Graeme Russ wrote: > On Tue, Aug 30, 2011 at 11:32 AM, Mike Frysinger wrote: > > On Monday, August 29, 2011 19:00:46 Graeme Russ wrote: > >> On Tue, Aug 30, 2011 at 6:10 AM, Mike Frysinger wrote: > >> > On Monday, August 29, 2011 15:42:23 Simon Glass wrote: > >> >> Yes I agree, although if you have more than 1KB of data it might be a > >> >> bug. > >> > >> I personally don't see the need - I expect the amount of pre-console > >> output would be faily limited considering that the board should do > >> everything it can to initialise console as early as possible. > > > > until people hit an early fail and add a lot of debug printf's and then > > the output gets silently clipped. it's confusing imo, and i say this > > having implemented early debug output in other systems (including linux) > > and seeing how people used/reacted to it. > > We can easily have a 'output clipped' so people know what happened and can > trim their debugging messages accordingly
much easier said than done. clipping the head rather than the tail is much more often the right default. > >> > give people a foot and they'll take 1MiB :p > >> > > >> > it's fairly easy as well: > >> > #define CIRC_BUF_IDX(idx) ((idx) & (CONFIG_SYS_TMP_CON_BUF_SZ-1)) > >> > buffer[CIRC_BUF_IDX(gd->conf_buf_idx++)] = c; > >> > >> But does that work for non power-of-two buffer sizes... > > > > no, but not that big of a deal. so you get limited to the last 1KiB, > > 4KiB, 8KiB, 16KiB, etc... amount of data. > > Until someone doesn't read the documentation and figures they can only > squeeze 200 bytes out of their L1 cache after making room for gd and stack > and then tries to print 201 bytes of debug info and trashes either the > stack or gd and then things start to get a lot weirder than simply having > their early debug messgaes clipped... this is really a non-issue as it's trivial to catch at CPP time: #if (CONFIG_SYS_TMP_CON_BUF_SZ & (CONFIG_SYS_TMP_CON_BUF_SZ - 1)) # error "CONFIG_SYS_TMP_CON_BUF_SZ must be a power-of-two" #endif > To be safe, CONFIG_SYS_TMP_CON_BUF_SZ would need to be checked for ^2 size > and now we only get 128 bytes rather than 200 :( - Better to add another > long in gd and get 196 my systems dont have nearly the size restrictions yours do, so if you think that's better, that's fine by me. i dont care so much about the internal implementation details of the circular buffer ... i only care that it is a circular buffer and not one that stops too soon. -mike
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