On Tue, Aug 23, 2011 at 1:12 PM, Wolfgang Denk wd@denx.de wrote:
Dear Anton Staaf,
In message CAF6FioXeFQP2a0VaZOVOTmxPvJxF4=kamS18=2=p6TFNefwUuA@mail.gmail.com you wrote:
what about adding a new func like: #define dma_buffer_alloca(size)
I generally avoid large allocations on the stack, they can confuse virtual stack management and blow out small embedded stacks. But neither of these are really a problem for most U-Boot targets. Are you thinking something like:
#define dma_buffer_alloca(size) alloca(size + get_dcache_line_size() -
- & ~(get_dcache_line_size() - 1);
I don't think I will accept any alloca() based code into mainline.
Ahh, that must have been my reason for not using it in the first place, a premonition. :)
So then, to guide our efforts, what is a more suitable solution? Would you prefer we stick with the existing path of calling memalign and passing it the cache size by directly calling get_dcache_line_size? Or would you prefer something more like a dma_buffer_malloc function that allocates on the heap a cache line size aligned buffer and returns it?
Hmm, that will require a bit of thought because we need to recover the original pointer returned by malloc to cleanly free the buffer later.
Thanks, Anton
Best regards,
Wolfgang Denk
-- DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd@denx.de "There are three principal ways to lose money: wine, women, and en- gineers. While the first two are more pleasant, the third is by far the more certain." -- Baron Rothschild, ca. 1800