Am Freitag, 9. April 2010 00:20:36 schrieb Alan Stern: > > > That would work, but it doesn't match the way existing drivers use the > > > interface. For example, the audio driver allocates a 16-byte coherent > > > buffer and then uses four bytes from it for each of four different > > > URBs. > > > > That will not work with any fallback that does not yield a coherent buffer. > > What you mean isn't entirely clear. But it certainly does work in > various circumstances that don't yield coherent buffers. For example, > it works if the controller uses PIO instead of DMA. It also works if > the controller uses DMA and the URBs have to be bounced. It'll work on x86. On incoherent architectures this violates the cacheline rules for DMA-mapping if you have to bounce. So it seems to me that if you want to share a buffer between URBs, it must be coherent. Regards Oliver -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
