Document the DMA descriptor `struct plx_dma_desc`, and the DMA abort
function `plx9080_abort_dma()`.
Signed-off-by: Ian Abbott <abbotti@xxxxxxxxx>
---
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 d701b15..f67f9d7 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;
--
2.8.1
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