usb: add a HCD_DMA flag instead of guestimating DMA capabilities

The usb core is the only major place in the kernel that checks for
a non-NULL device dma_mask to see if a device is DMA capable.  This
is generally a bad idea, as all major busses always set up a DMA mask,
even if the device is not DMA capable - in fact bus layers like PCI
can't even know if a device is DMA capable at enumeration time.  This
leads to lots of workaround in HCD drivers, and also prevented us from
setting up a DMA mask for platform devices by default last time we
tried.

Replace this guess with an explicit HCD_DMA that is set by drivers that
appear to have DMA support.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20190816062435.881-4-hch@lst.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 5 insertions, 2 deletions

diff --git a/include/linux/usb/hcd.h b/include/linux/usb/hcd.h
index a20e7815d814..8d3869c7de85 100644
--- a/include/linux/usb/hcd.h
+++ b/include/linux/usb/hcd.h
@@ -256,6 +256,7 @@ struct hc_driver {
 
         int     flags;
 #define HCD_MEMORY      0x0001          /* HC regs use memory (else I/O) */
+#define HCD_DMA         0x0002          /* HC uses DMA */
 #define HCD_SHARED      0x0004          /* Two (or more) usb_hcds share HW */
 #define HCD_USB11       0x0010          /* USB 1.1 */
 #define HCD_USB2        0x0020          /* USB 2.0 */
@@ -422,8 +423,10 @@ static inline bool hcd_periodic_completion_in_progress(struct usb_hcd *hcd,
         return hcd->high_prio_bh.completing_ep == ep;
 }
 
-#define hcd_uses_dma(hcd) \
-        (IS_ENABLED(CONFIG_HAS_DMA) && (hcd)->self.uses_dma)
+static inline bool hcd_uses_dma(struct usb_hcd *hcd)
+{
+        return IS_ENABLED(CONFIG_HAS_DMA) && (hcd->driver->flags & HCD_DMA);
+}
 
 extern int usb_hcd_link_urb_to_ep(struct usb_hcd *hcd, struct urb *urb);
 extern int usb_hcd_check_unlink_urb(struct usb_hcd *hcd, struct urb *urb,