[lhcs-devel] Re: [RFC] don't create cpu/online sysfs file

[Ashok Raj]

On Sun, Jun 06, 2004 at 10:05:35PM -0700, Dave Hansen wrote:
> I like that patch a lot.  It certainly removes any argument about
> function names :)
>
> Can we maybe change the name of the new field a bit?

I strategically (?) changed the name to not_removable, so the field name
can indicate the purpose as well clearly. Oh well, i changed the field name
to no_control, to indicate "not to create" a control file. the "can_remove"
when i read it in isolation, seems to indicate "this cpu is removable" and
for correcness i think we would change the normal case to set as 1 instead.

picky picky picky :-)

i added a note in the function doc as well for clarity.



Signed-off-by: Ashok Raj <ashok.raj at intel.com>

D: This file provides ability for caller of register_cpu() to either create
D: a control file, or not. This can be handy if a particular platform decides
D: that certain CPU's are not removable. Hence would like to not create
D: a control file.


---

 linux-2.6.7-rc2-root/arch/ppc64/kernel/sysfs.c |   10 ++++++++++
 linux-2.6.7-rc2-root/drivers/base/cpu.c        |    4 +++-
 linux-2.6.7-rc2-root/include/linux/cpu.h       |    1 +
 3 files changed, 14 insertions(+), 1 deletion(-)

diff -puN include/linux/cpu.h~cpu_control_file include/linux/cpu.h
--- linux-2.6.7-rc2/include/linux/cpu.h~cpu_control_file	2004-06-06 12:54:02.319017387 -0700
+++ linux-2.6.7-rc2-root/include/linux/cpu.h	2004-06-07 06:25:44.667732023 -0700
@@ -27,6 +27,7 @@

 struct cpu {
 	int node_id;		/* The node which contains the CPU */
+	int no_control;		/* Should the sysfs control file be created? */
 	struct sys_device sysdev;
 };

diff -puN drivers/base/cpu.c~cpu_control_file drivers/base/cpu.c
--- linux-2.6.7-rc2/drivers/base/cpu.c~cpu_control_file	2004-06-06 12:56:47.349375320 -0700
+++ linux-2.6.7-rc2-root/drivers/base/cpu.c	2004-06-07 07:03:12.624937664 -0700
@@ -58,6 +58,8 @@ static inline void register_cpu_control(

 /*
  * register_cpu - Setup a driverfs device for a CPU.
+ * @cpu - Callers can set the cpu->no_control field to 1, to indicate not to
+ *		  generate a control file in sysfs for this CPU.
  * @num - CPU number to use when creating the device.
  *
  * Initialize and register the CPU device.
@@ -75,7 +77,7 @@ int __init register_cpu(struct cpu *cpu,
 		error = sysfs_create_link(&root->sysdev.kobj,
 					  &cpu->sysdev.kobj,
 					  kobject_name(&cpu->sysdev.kobj));
-	if (!error)
+	if (!error && !cpu->no_control)
 		register_cpu_control(cpu);
 	return error;
 }
diff -puN arch/ppc64/kernel/sysfs.c~cpu_control_file arch/ppc64/kernel/sysfs.c
--- linux-2.6.7-rc2/arch/ppc64/kernel/sysfs.c~cpu_control_file	2004-06-06 13:12:06.467033408 -0700
+++ linux-2.6.7-rc2-root/arch/ppc64/kernel/sysfs.c	2004-06-07 06:29:35.126834393 -0700
@@ -325,6 +325,16 @@ static int __init topology_init(void)
 #ifdef CONFIG_NUMA
 		parent = &node_devices[cpu_to_node(cpu)];
 #endif
+		/*
+		 * For now, we just see if the system supports making
+		 * the RTAS calls for CPU hotplug.  But, there may be a
+		 * more comprehensive way to do this for an individual
+		 * CPU.  For instance, the boot cpu might never be valid
+		 * for hotplugging.
+		 */
+		if (systemcfg->platform == PLATFORM_PSERIES_LPAR)
+			cpu->no_control=1;
+
 		register_cpu(c, cpu, parent);

 		register_cpu_pmc(&c->sysdev);

_

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