Hi Geert, On 17.01.2020 16:30, Geert Uytterhoeven wrote: > Currently it is not easy to find out which DMA channels are in use, and > which slave devices are using which channels. > > Fix this by creating two symlinks between the DMA channel and the actual > slave device when a channel is requested: > 1. A "slave" symlink from DMA channel to slave device, > 2. A "dma:<name>" symlink slave device to DMA channel. > When the channel is released, the symlinks are removed again. > The latter requires keeping track of the slave device and the channel > name in the dma_chan structure. > > Note that this is limited to channel request functions for requesting an > exclusive slave channel that take a device pointer (dma_request_chan() > and dma_request_slave_channel*()). > > Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx> > Tested-by: Niklas Söderlund <niklas.soderlund@xxxxxxxxxxxx> This patch breaks booting on almost all Exynos based boards: https://lore.kernel.org/linux-samsung-soc/20200129161113.GE3928@xxxxxxxxxxxxx/T/#u I've already sent a fix: https://lkml.org/lkml/2020/1/29/498 BTW, this patch reminds me some of my earlier work: https://www.mail-archive.com/linux-kernel@xxxxxxxxxxxxxxx/msg1329778.html I had similar need to keep a client's struct device pointer for every requested channel, but it turned out to be much more complicated than I've initially thought. I've abandoned that, due to lack of time, but maybe some of that discussion and concerns are still valid (I hope that links to earlier versions are still working)... > ... Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland
