genirq: Expose irq_desc->node in proc/irq

Expose irq_desc->node as /proc/irq/*/node.

This file provides device hardware locality information for apps
desiring to include hardware locality in irq mapping decisions.

Signed-off-by: Dimitri Sivanich <sivanich@sgi.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

2 files changed, 27 insertions, 0 deletions

diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index a4f30faa4f1f..6507d2ae5236 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -566,6 +566,10 @@ The default_smp_affinity mask applies to all non-active IRQs, which are the
 IRQs which have not yet been allocated/activated, and hence which lack a
 /proc/irq/[0-9]* directory.
 
+The node file on an SMP system shows the node to which the device using the IRQ
+reports itself as being attached. This hardware locality information does not
+include information about any possible driver locality preference.
+
 prof_cpu_mask specifies which CPUs are to be profiled by the system wide
 profiler. Default value is ffffffff (all cpus).
 
diff --git a/kernel/irq/proc.c b/kernel/irq/proc.c
index 6f50eccc79c0..e346e08f5c34 100644
--- a/kernel/irq/proc.c
+++ b/kernel/irq/proc.c
@@ -146,6 +146,26 @@ static const struct file_operations default_affinity_proc_fops = {
         .release        = single_release,
         .write          = default_affinity_write,
 };
+
+static int irq_node_proc_show(struct seq_file *m, void *v)
+{
+        struct irq_desc *desc = irq_to_desc((long) m->private);
+
+        seq_printf(m, "%d\n", desc->node);
+        return 0;
+}
+
+static int irq_node_proc_open(struct inode *inode, struct file *file)
+{
+        return single_open(file, irq_node_proc_show, PDE(inode)->data);
+}
+
+static const struct file_operations irq_node_proc_fops = {
+        .open           = irq_node_proc_open,
+        .read           = seq_read,
+        .llseek         = seq_lseek,
+        .release        = single_release,
+};
 #endif
 
 static int irq_spurious_proc_show(struct seq_file *m, void *v)
@@ -230,6 +250,9 @@ void register_irq_proc(unsigned int irq, struct irq_desc *desc)
         /* create /proc/irq/<irq>/smp_affinity */
         proc_create_data("smp_affinity", 0600, desc->dir,
                          &irq_affinity_proc_fops, (void *)(long)irq);
+
+        proc_create_data("node", 0444, desc->dir,
+                         &irq_node_proc_fops, (void *)(long)irq);
 #endif
 
         proc_create_data("spurious", 0444, desc->dir,