On Wed, 27 Feb 2008 11:23:26 +0100 Marcin Slusarz <[EMAIL PROTECTED]> wrote:
> On Tue, Feb 26, 2008 at 11:23:20PM +0100, Jean Delvare wrote: > > Hi Marcin, > Hi > > > On Tue, 26 Feb 2008 22:03:16 +0100, Marcin Slusarz wrote: > > > Do you have an idea (or patch :D) how to solve this: > > > 0x00000234 v4l_compat_translate_ioctl [v4l1-compat]: 1376 > > > ? That's on top of my make checkstack output > > > > Random ideas (but I am in no way a specialist of this exercise): > > > > * You could try moving the structures to the blocks where they are used, > > in the case a given structure is used for only one ioctl. I'm not too > > sure how gcc handles local variables declared inside blocks with > > regards to stack reservation though. I thought it would work but my > > experiments today seem to suggest it doesn't. > That won't work. Variables at beginning of function take only ~600 bytes, > so the rest must be from inner blocks and inlines (probably). > > > * You can move the handling of some ioctls to dedicated functions, just > > like I did in i2c-dev: > > http://lists.lm-sensors.org/pipermail/i2c/2008-February/003010.html > > However there is a risk that gcc will inline these functions (that's > > what happened to me...) Not sure how to prevent gcc from inlining. > There's "noinline" attribute in linux/compiler.h (compiler-gcc.h actually) > for these situations. > > > * You can allocate the structures dynamically, as you originally wanted > > to do for ir-kbd-i2c. However this has a performance penalty and will > > fragment the memory, so it's not ideal. > > > > * If each ioctl uses only one of the structures, you may define a union > > of all the structures. The size of the union will be the size of the > > biggest structure, so you save a lot of space on the stack. > Nice idea. > > I'll try 2nd and 4th approaches. The union will probably solve. This function is very complex, since it needs to deal with almost all v4l1 v4l2 ioctls (about 80-90). Splitting into small functions might help, but probably, gcc will create the functions as inline. > > Marcin Slusarz Cheers, Mauro _______________________________________________ i2c mailing list [email protected] http://lists.lm-sensors.org/mailman/listinfo/i2c
