dma-debug: add dma_debug_driver kernel command line

This patch add the dma_debug_driver= boot parameter to enable the driver
filter for early boot.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

2 files changed, 25 insertions, 0 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index e87bdbfbcc75..b3f1314588c9 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -646,6 +646,13 @@ and is between 256 and 4096 characters. It is defined in the file
                         DMA-API debugging code disables itself because the
                         architectural default is too low.
 
+        dma_debug_driver=<driver_name>
+                        With this option the DMA-API debugging driver
+                        filter feature can be enabled at boot time. Just
+                        pass the driver to filter for as the parameter.
+                        The filter can be disabled or changed to another
+                        driver later using sysfs.
+
         dscc4.setup=    [NET]
 
         dtc3181e=       [HW,SCSI]
diff --git a/lib/dma-debug.c b/lib/dma-debug.c
index c6330b1a7be7..d0618aa13b49 100644
--- a/lib/dma-debug.c
+++ b/lib/dma-debug.c
@@ -1109,3 +1109,21 @@ void debug_dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg,
 }
 EXPORT_SYMBOL(debug_dma_sync_sg_for_device);
 
+static int __init dma_debug_driver_setup(char *str)
+{
+        int i;
+
+        for (i = 0; i < NAME_MAX_LEN - 1; ++i, ++str) {
+                current_driver_name[i] = *str;
+                if (*str == 0)
+                        break;
+        }
+
+        if (current_driver_name[0])
+                printk(KERN_INFO "DMA-API: enable driver filter for "
+                                 "driver [%s]\n", current_driver_name);
+
+
+        return 1;
+}
+__setup("dma_debug_driver=", dma_debug_driver_setup);