ide: filter out "default" transfer mode values in set_xfer_rate()

* Filter out "default" transfer mode values (0x00 - default PIO mode,
  0x01 - default PIO mode w/ IORDY disabled) in write handler for obsoleted
  /proc/ide/hd?/settings:current_speed setting.

  Allowing "default" transfer mode values is a dangerous thing to do as
  we don't support programming controller to the "default" transfer mode
  and devices often use different values for the default and maximum PIO
  mode (i.e. PIO2 default and PIO4 maximum) so the controller will stay
  programmed for higher PIO mode while device will use the lower PIO mode.

  There is no functionality loss as by using special IOCTLs device can
  still be programmed to "default" transfer modes (it is only useful for
  debugging/testing purposes anyway).

* Remove no longer needed IDE_HFLAG_ABUSE_SET_DMA_MODE host flag, it was
  previously used by few host drivers to program the controller to PIO0
  timings for "default" transfer mode == 0x01 (although some host drivers
  would program invalid PIO timings instead).

* Cleanup ide_set_xfer_rate() and add BUG_ON().

Suggested-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>

1 files changed, 2 insertions, 13 deletions

diff --git a/drivers/ide/ide-lib.c b/drivers/ide/ide-lib.c
index 13af72f09ec4..7ac44d515470 100644
--- a/drivers/ide/ide-lib.c
+++ b/drivers/ide/ide-lib.c
@@ -266,22 +266,11 @@ int ide_set_xfer_rate(ide_drive_t *drive, u8 rate)
 
         rate = ide_rate_filter(drive, rate);
 
+        BUG_ON(rate < XFER_PIO_0);
+
         if (rate >= XFER_PIO_0 && rate <= XFER_PIO_5)
                 return ide_set_pio_mode(drive, rate);
 
-        /*
-         * TODO: transfer modes 0x00-0x07 passed from the user-space are
-         * currently handled here which needs fixing (please note that such
-         * case could happen iff the transfer mode has already been set on
-         * the device by ide-proc.c::set_xfer_rate()).
-         */
-        if (rate < XFER_PIO_0) {
-                if (hwif->host_flags & IDE_HFLAG_ABUSE_SET_DMA_MODE)
-                        return ide_set_dma_mode(drive, rate);
-                else
-                        return ide_config_drive_speed(drive, rate);
-        }
-
         return ide_set_dma_mode(drive, rate);
 }