Mauro: You are reading too much into that comment. I never said it was valid to do what had been done, only that for the longest time this is what the driver did and it never caused a problem that I was made aware of. What I said there was correct, that this is what the driver had been doing in the past, that it's definitely causing a problem now and thus that is why this patch exists. I'd really rather you not mess with my comment. Probably too late however. -Mike On Fri, 21 May 2010, Mauro Carvalho Chehab wrote: > Mike Isely wrote: > > Please from http://linuxtv.org/hg/~mcisely/pvrusb2-patches for the > > following pvrusb2 driver fixes / improvements: > > > > - pvrusb2: Minor debug code fixup > > - pvrusb2: Fix Gotview hardware support > > - pvrusb2: Avoid using stack allocated buffers when performing USB I/O > > Your comment for this patch is wrong: > > pvrusb2: The pvrusb2 driver has for the longest time used a (tiny) > stack allocated buffer for some of its I/O with the hardware. > Apparently later kernels don't like this behavior and trap it at > run-time, causing nasty complaints to the kernel log. This trivial > change fixes the one case in the driver where this had been happening. > > It were never valid to use stack for DMA, as kernel provides > no warranty that the stack would be on a page that can do DMA. > In a matter of fact, as most x86 USB drivers accept DMA at the first > 3Gb of RAM space, this bug is generally not noticed on i386/x86_64 > archs. Yet, if your machine has more than 3Gb, there are some chances that > the stack would be at the HIGHMEM area, where DMA is not supported by the > processor. > > As this is a common error, newer kernels have some instrumentation support to > warn about such troubles. > > I'll be fixing the comment. > > > -- Mike Isely isely @ isely (dot) net PGP: 03 54 43 4D 75 E5 CC 92 71 16 01 E2 B5 F5 C1 E8 -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
