mmiotrace: print header using the read hook.

Now the header is printed only for `trace_pipe' file.

Signed-off-by: Pekka Paalanen <pq@iki.fi>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 53 insertions, 7 deletions

diff --git a/kernel/trace/trace_mmiotrace.c b/kernel/trace/trace_mmiotrace.c
index 79be4a18ec1e..6d2edbdde939 100644
--- a/kernel/trace/trace_mmiotrace.c
+++ b/kernel/trace/trace_mmiotrace.c
@@ -12,6 +12,10 @@
 
 #include "trace.h"
 
+struct header_iter {
+        struct pci_dev *dev;
+};
+
 static struct trace_array *mmio_trace_array;
 
 static void mmio_reset_data(struct trace_array *tr)
@@ -89,17 +93,57 @@ static int mmio_print_pcidev(struct trace_seq *s, const struct pci_dev *dev)
         return ret;
 }
 
-/* XXX: This is not called for trace_pipe file! */
-static void mmio_print_header(struct trace_iterator *iter)
+static void destroy_header_iter(struct header_iter *hiter)
+{
+        if (!hiter)
+                return;
+        pci_dev_put(hiter->dev);
+        kfree(hiter);
+}
+
+static void mmio_pipe_open(struct trace_iterator *iter)
 {
+        struct header_iter *hiter;
         struct trace_seq *s = &iter->seq;
-        struct pci_dev *dev = NULL;
 
         trace_seq_printf(s, "VERSION 20070824\n");
 
-        for_each_pci_dev(dev)
-                mmio_print_pcidev(s, dev);
-        /* XXX: return value? What if header is very long? */
+        hiter = kzalloc(sizeof(*hiter), GFP_KERNEL);
+        if (!hiter)
+                return;
+
+        hiter->dev = pci_get_device(PCI_ANY_ID, PCI_ANY_ID, NULL);
+        iter->private = hiter;
+}
+
+/* XXX: This is not called when the pipe is closed! */
+static void mmio_close(struct trace_iterator *iter)
+{
+        struct header_iter *hiter = iter->private;
+        destroy_header_iter(hiter);
+        iter->private = NULL;
+}
+
+static ssize_t mmio_read(struct trace_iterator *iter, struct file *filp,
+                                char __user *ubuf, size_t cnt, loff_t *ppos)
+{
+        ssize_t ret;
+        struct header_iter *hiter = iter->private;
+        struct trace_seq *s = &iter->seq;
+
+        if (!hiter)
+                return 0;
+
+        mmio_print_pcidev(s, hiter->dev);
+        hiter->dev = pci_get_device(PCI_ANY_ID, PCI_ANY_ID, hiter->dev);
+
+        if (!hiter->dev) {
+                destroy_header_iter(hiter);
+                iter->private = NULL;
+        }
+
+        ret = trace_seq_to_user(s, ubuf, cnt);
+        return (ret == -EBUSY) ? 0 : ret;
 }
 
 static int mmio_print_rw(struct trace_iterator *iter)
@@ -190,7 +234,9 @@ static struct tracer mmio_tracer __read_mostly =
         .name           = "mmiotrace",
         .init           = mmio_trace_init,
         .reset          = mmio_trace_reset,
-        .open           = mmio_print_header,
+        .pipe_open      = mmio_pipe_open,
+        .close          = mmio_close,
+        .read           = mmio_read,
         .ctrl_update    = mmio_trace_ctrl_update,
         .print_line     = mmio_print_line,
 };