From 6a64877f6318c6db63beb5ae1397c8afc09e8628 Mon Sep 17 00:00:00 2001 From: Ian Abbott Date: Fri, 20 May 2016 14:49:21 +0100 Subject: [PATCH] staging: comedi: plx9080.h: Add kerneldoc comments Document the DMA descriptor `struct plx_dma_desc`, and the DMA abort function `plx9080_abort_dma()`. Signed-off-by: Ian Abbott Signed-off-by: Greg Kroah-Hartman --- drivers/staging/comedi/drivers/plx9080.h | 35 ++++++++++++++++++++---- 1 file changed, 29 insertions(+), 6 deletions(-) diff --git a/drivers/staging/comedi/drivers/plx9080.h b/drivers/staging/comedi/drivers/plx9080.h index d701b15afc84..f67f9d732828 100644 --- a/drivers/staging/comedi/drivers/plx9080.h +++ b/drivers/staging/comedi/drivers/plx9080.h @@ -19,16 +19,27 @@ #ifndef __COMEDI_PLX9080_H #define __COMEDI_PLX9080_H -/* descriptor block used for chained dma transfers */ +/** + * struct plx_dma_desc - DMA descriptor format for PLX PCI 9080 + * @pci_start_addr: PCI Bus address for transfer (DMAPADR). + * @local_start_addr: Local Bus address for transfer (DMALADR). + * @transfer_size: Transfer size in bytes (max 8 MiB) (DMASIZ). + * @next: Address of next descriptor + flags (DMADPR). + * + * Describes the format of a scatter-gather DMA descriptor for the PLX + * PCI 9080. All members are raw, little-endian register values that + * will be transferred by the DMA engine from local or PCI memory into + * corresponding registers for the DMA channel. + * + * The DMA descriptors must be aligned on a 16-byte boundary. Bits 3:0 + * of @next contain flags describing the address space of the next + * descriptor (local or PCI), an "end of chain" marker, an "interrupt on + * terminal count" bit, and a data transfer direction. + */ struct plx_dma_desc { __le32 pci_start_addr; __le32 local_start_addr; - /* transfer_size is in bytes, only first 23 bits of register are used */ __le32 transfer_size; - /* - * address of next descriptor (quad word aligned), plus some - * additional bits (see PLX_REG_DMADPR) - */ __le32 next; }; @@ -594,6 +605,18 @@ struct plx_dma_desc { #define PLX_PREFETCH 32 +/** + * plx9080_abort_dma - Abort a PLX PCI 9080 DMA transfer + * @iobase: Remapped base address of configuration registers. + * @channel: DMA channel number (0 or 1). + * + * Aborts the DMA transfer on the channel, which must have been enabled + * and started beforehand. + * + * Return: + * %0 on success. + * -%ETIMEDOUT if timed out waiting for abort to complete. + */ static inline int plx9080_abort_dma(void __iomem *iobase, unsigned int channel) { void __iomem *dma_cs_addr; -- 2.20.1