On Mon, Oct 7, 2013 at 12:58 PM, Rajat Jain <rajatjain@xxxxxxxxxxx> wrote: > Hello Bjorn / Eric / Folks, > > This is to seek suggestions about a problem I'm trying to solve. > > The problem > =========== > 1) My company makes routers that have hot-pluggable cards with PCI express interfaces on them. We need to be able to hot-plug those cards, however the cards or the slots do not have the fancy bells & whistles (hot plug elements like MRL, sensor, attention button etc), and hence the hot-plug signals from the PCIe switch aren't really connected. The elements you mention are optional per the spec (PCIe r3.0, sec 6.7.1). The lack of them, by itself, should not be enough to force you to write a new hotplug driver. pciehp is used for ExpressCard hotplug, and that's a similar situation where there's no MRL, no MRL sensor, no interlock, no attention button, etc. What connects the hot-pluggable card to the system? PCI? PCIe? Something else? If it's PCIe, it seems like you'd make your life simpler by taking advantage of some or all of the hotplug support that is likely in the PCIe Root Port or Downstream Port leading to the slot. > 2) In addition to the above, we have onboard ASICs that are reachable via the PCIe. However, as part of regular operation of a router (e.g. user wants to switch off some ports), the ASICs can be off-lined / on-lined via out-of-band HW pins. The result is that we could see the PCIe link go down or up to that ASIC. This can be thought of as a "virtual" hot-plug of ASIC devices. Since the ASICs are themselves on the board, there is really no slot, and the HP signals again do not make much sense in this case. It doesn't really matter that there's no physical slot and the user can't replace an ASIC with a different one. You can still use the hotplug signals that *are* relevant, e.g., it sounds like things related to Hot-Plug Surprise, Presence Detect, and Data Link Layer State would still make sense. The current pciehp driver doesn't really do anything with the Data Link Layer State Changed Enable bit (it looks like we *disable* that notification, but never *enable* it). It sounds like a reasonable thing to add to pciehp, though. Bjorn -- To unsubscribe from this list: send the line "unsubscribe linux-hotplug" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
