From: Wolfram Sang <wsa@xxxxxxxxxxxxx> So, after revisiting old mail threads and taking part in a similar discussion on the USB list, here is an RFC on what I cooked together regarding DMA and I2C in the Linux world. I documented my reasoning with patch 2 which mentions a helper function which gets added with patch 1. Patch 3 shows a super simple example with the i2c-sh_mobile driver. And patch 4 shows a super complicated example with the i2c-rcar driver. But it is nice to have such a corner case already in the beginning of development. Please let me know what you think. What I surely plan to add until next time is to fix two central places in the I2C core where the data buffer for block transfers is currently put on the stack. A branch can be found here: git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux.git renesas/topic/i2c-core-dma And big kudos to Renesas Electronics for funding this work, thank you very much! Regards, Wolfram Wolfram Sang (4): i2c: add helper to determine if DMA is favoured i2c: add docs to clarify DMA handling i2c: sh_mobile: use helper to decide if DMA is used i2c: rcar: check for DMA-capable buffers Documentation/i2c/DMA-considerations | 28 ++++++++++++++++++++++++++++ drivers/i2c/busses/i2c-rcar.c | 18 +++++++++++++----- drivers/i2c/busses/i2c-sh_mobile.c | 2 +- include/linux/i2c.h | 29 +++++++++++++++++++++++++++++ 4 files changed, 71 insertions(+), 6 deletions(-) create mode 100644 Documentation/i2c/DMA-considerations -- 2.11.0
