For streaming acquisition on the analog input subdevice, this driver normally uses DMA double buffering into two internal DMA buffers, so it can switch buffers early after a DMA transfer has completed, while it processes the completed DMA buffer. PATCH 1 is just a bit of tidy up. PATCH 2 avoids switching the DMA double buffer at the end of acquisition. For DMA single buffering, it avoids restarting the DMA transfer if acquisition has ended normally or due to a comedi buffer overflow error. (However, for double buffering, the DMA transfer has already been started on the other DMA buffer and will be stopped soon after.) PATCH 3 eliminates a possible defragmentation step in the DMA buffer contents before they are transferred to the comedi buffer. Instead, the DMA buffer fragments are copied directly to the comedi buffer, or is copied all in one go if the data is not fragmented. This work is in response to Hartley's "PATCH 4/4] staging: comedi: adl_pci9118: switch DMA buffers after writing samples", dated Mon, 10 Nov 2014 1959:17 -0500, message ID <1415667477-28403-5-git-send-email-hsweeten@xxxxxxxxxxxxxxxxxxx>, which was not applied. These patches are against Greg's "staging-testing" branch. 1) staging: comedi: adl_pci9118: simplify interrupt_pci9118_ai_dma() a bit 2) staging: comedi: adl_pci9118: try and avoid unnecessary DMA restart 3) staging: comedi: adl_pci9118: eliminate DMA buffer defragmentation step drivers/staging/comedi/drivers/adl_pci9118.c | 157 +++++++++++++++++++++------ 1 file changed, 121 insertions(+), 36 deletions(-) _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
