staging: comedi: work without HAS_DMA

The core "comedi" module and the "mite" helper module for NI PCI devices
both have calls to `dma_alloc_coherent()` and `dma_free_coherent()`.
Those functions are only available if `CONFIG_HAS_DMA` is defined.

Apart from the "mite" module, the functions are only called for comedi
drivers that set `s->async_dma_dir` (where `s` is a pointer to a `struct
comedi_subdevice`) to anything other than `DMA_NONE`.

Change local helper functions `__comedi_buf_alloc()` and
`__comedi_buf_free()` to only call `dma_alloc_coherent()` and
`dma_free_coherent()` if `CONFIG_HAS_DMA` is defined.

Change the "Kconfig" to make the following configuration options depend
on `HAS_DMA`:

`COMEDI_MITE` - builds the "mite" module.
`COMEDI_NI_6527` - selects `COMEDI_MITE`.
`COMEDI_NI_65XX` - selects `COMEDI_MITE`.
`COMEDI_NI_670X` - selects `COMEDI_MITE`.
`COMEDI_NI_LABPC_PCI` - selects `COMEDI_MITE`.
`COMEDI_NI_PCIDIO` - selects `COMEDI_MITE`.
`COMEDI_NI_TIOCMD` - selects `COMEDI_MITE`.
`COMEDI_NI_660X` - selects `COMEDI_NI_TIOCMD`,
                   sets `s->async_dma_dir`.
`COMEDI_NI_PCIMIO` - selects `COMEDI_NI_TIOCMD`,
                     sets `s->async_dma_dir`.
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/Kconfig

@@ -981,6 +981,7 @@ config COMEDI_ME_DAQ
 
 config COMEDI_NI_6527
 	tristate "NI 6527 support"
+	depends on HAS_DMA
 	select COMEDI_MITE
 	---help---
 	  Enable support for the National Instruments 6527 PCI card
@@ -990,6 +991,7 @@ config COMEDI_NI_6527
 
 config COMEDI_NI_65XX
 	tristate "NI 65xx static dio PCI card support"
+	depends on HAS_DMA
 	select COMEDI_MITE
 	---help---
 	  Enable support for National Instruments 65xx static dio boards.
@@ -1003,6 +1005,7 @@ config COMEDI_NI_65XX
 
 config COMEDI_NI_660X
 	tristate "NI 660x counter/timer PCI card support"
+	depends on HAS_DMA
 	select COMEDI_NI_TIOCMD
 	---help---
 	  Enable support for National Instruments PCI-6601 (ni_660x), PCI-6602,
@@ -1013,6 +1016,7 @@ config COMEDI_NI_660X
 
 config COMEDI_NI_670X
 	tristate "NI 670x PCI card support"
+	depends on HAS_DMA
 	select COMEDI_MITE
 	---help---
 	  Enable support for National Instruments PCI-6703 and PCI-6704
@@ -1022,6 +1026,7 @@ config COMEDI_NI_670X
 
 config COMEDI_NI_LABPC_PCI
 	tristate "NI Lab-PC PCI-1200 support"
+	depends on HAS_DMA
 	select COMEDI_NI_LABPC
 	select COMEDI_MITE
 	---help---
@@ -1032,6 +1037,7 @@ config COMEDI_NI_LABPC_PCI
 
 config COMEDI_NI_PCIDIO
 	tristate "NI PCI-DIO32HS, PCI-6533, PCI-6534 support"
+	depends on HAS_DMA
 	select COMEDI_MITE
 	select COMEDI_8255
 	---help---
@@ -1043,6 +1049,7 @@ config COMEDI_NI_PCIDIO
 
 config COMEDI_NI_PCIMIO
 	tristate "NI PCI-MIO-E series and M series support"
+	depends on HAS_DMA
 	select COMEDI_NI_TIOCMD
 	select COMEDI_8255
 	select COMEDI_FC
@@ -1095,10 +1102,12 @@ config COMEDI_SSV_DNP
 	  called ssv_dnp.
 
 config COMEDI_MITE
+	depends on HAS_DMA
 	tristate
 
 config COMEDI_NI_TIOCMD
 	tristate
+	depends on HAS_DMA
 	select COMEDI_NI_TIO
 	select COMEDI_MITE
 

drivers/staging/comedi/comedi_buf.c

@@ -51,10 +51,12 @@ static void __comedi_buf_free(struct comedi_device *dev,
 			clear_bit(PG_reserved,
 				  &(virt_to_page(buf->virt_addr)->flags));
 			if (s->async_dma_dir != DMA_NONE) {
+#ifdef CONFIG_HAS_DMA
 				dma_free_coherent(dev->hw_dev,
 						  PAGE_SIZE,
 						  buf->virt_addr,
 						  buf->dma_addr);
+#endif
 			} else {
 				free_page((unsigned long)buf->virt_addr);
 			}
@@ -84,11 +86,15 @@ static void __comedi_buf_alloc(struct comedi_device *dev,
 	for (i = 0; i < n_pages; i++) {
 		buf = &async->buf_page_list[i];
 		if (s->async_dma_dir != DMA_NONE)
+#ifdef CONFIG_HAS_DMA
 			buf->virt_addr = dma_alloc_coherent(dev->hw_dev,
 							    PAGE_SIZE,
 							    &buf->dma_addr,
 							    GFP_KERNEL |
 							    __GFP_COMP);
+#else
+			break;
+#endif
 		else
 			buf->virt_addr = (void *)get_zeroed_page(GFP_KERNEL);
 		if (!buf->virt_addr)