floppy: tolerate DMA channel unavailability

The floppy driver is already written to be able to operate in virtual DMA
mode.  Thus it can easily be adjusted to tolerate failure from
fd_request_dma() as long as virtual DMA mode is not disallowed.

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 9 insertions, 5 deletions

diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
index 80483aac4cc9..72803a3585ff 100644
--- a/drivers/block/floppy.c
+++ b/drivers/block/floppy.c
@@ -4388,11 +4388,15 @@ static int floppy_grab_irq_and_dma(void)
         if (fd_request_dma()) {
                 DPRINT("Unable to grab DMA%d for the floppy driver\n",
                        FLOPPY_DMA);
-                fd_free_irq();
-                spin_lock_irqsave(&floppy_usage_lock, flags);
-                usage_count--;
-                spin_unlock_irqrestore(&floppy_usage_lock, flags);
-                return -1;
+                if (can_use_virtual_dma & 2)
+                        use_virtual_dma = can_use_virtual_dma = 1;
+                if (!(can_use_virtual_dma & 1)) {
+                        fd_free_irq();
+                        spin_lock_irqsave(&floppy_usage_lock, flags);
+                        usage_count--;
+                        spin_unlock_irqrestore(&floppy_usage_lock, flags);
+                        return -1;
+                }
         }
 
         for (fdc = 0; fdc < N_FDC; fdc++) {