On Tue, 2013-01-29 at 23:58 -0500, Greg KH wrote:
> On Thu, Jan 10, 2013 at 04:40:19PM -0700, Toshi Kani wrote:
> > +/*
> > + * Hot-plug device information
> > + */
>
> Again, stop it with the "generic" hotplug term here, and everywhere
> else. You are doing a very _specific_ type of hotplug devices, so spell
> it out. We've worked hard to hotplug _everything_ in Linux, you are
> going to confuse a lot of people with this type of terms.
Agreed. I will clarify in all places.
> > +union shp_dev_info {
> > + struct shp_cpu {
> > + u32 cpu_id;
> > + } cpu;
>
> What is this? Why not point to the system device for the cpu?
This info is used to on-line a new CPU and create its system/cpu device.
In other word, a system/cpu device is created as a result of CPU
hotplug.
> > + struct shp_memory {
> > + int node;
> > + u64 start_addr;
> > + u64 length;
> > + } mem;
>
> Same here, why not point to the system device?
Same as above.
> > + struct shp_hostbridge {
> > + } hb;
> > +
> > + struct shp_node {
> > + } node;
>
> What happened here with these? Empty structures? Huh?
They are place holders for now. PCI bridge hot-plug and node hot-plug
are still very much work in progress, so I have not integrated them into
this framework yet.
> > +};
> > +
> > +struct shp_device {
> > + struct list_head list;
> > + struct device *device;
>
> No, make it a "real" device, embed the device into it.
This device pointer is used to send KOBJ_ONLINE/OFFLINE event during CPU
online/offline operation in order to maintain the current behavior. CPU
online/offline operation only changes the state of CPU, so its
system/cpu device continues to be present before and after an operation.
(Whereas, CPU hot-add/delete operation creates or removes a system/cpu
device.) So, this "*device" needs to be a pointer to reference an
existing device that is to be on-lined/off-lined.
> But, again, I'm going to ask why you aren't using the existing cpu /
> memory / bridge / node devices that we have in the kernel. Please use
> them, or give me a _really_ good reason why they will not work.
We cannot use the existing system devices or ACPI devices here. During
hot-plug, ACPI handler sets this shp_device info, so that cpu and memory
handlers (drivers/cpu.c and mm/memory_hotplug.c) can obtain their target
device information in a platform-neutral way. During hot-add, we first
creates an ACPI device node (i.e. device under /sys/bus/acpi/devices),
but platform-neutral modules cannot use them as they are ACPI-specific.
Also, its system device (i.e. device under /sys/devices/system) has not
been created until the hot-add operation completes.
> > + enum shp_class class;
> > + union shp_dev_info info;
> > +};
> > +
> > +/*
> > + * Hot-plug request
> > + */
> > +struct shp_request {
> > + /* common info */
> > + enum shp_operation operation; /* operation */
> > +
> > + /* hot-plug event info: only valid for hot-plug operations */
> > + void *handle; /* FW handle */
> > + u32 event; /* FW event */
>
> What is this?
The shp_request describes a hotplug or online/offline operation that is
requested. In case of hot-plug request, the "*handle" describes a
target device (which is an ACPI device object) and the "event" describes
a type of request, such as hot-add or hot-delete.
Thanks,
-Toshi
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