Hello Greg / All, Replying on this thread as I have a small query left regarding this... > -----Original Message----- > From: Greg KH [mailto:greg@xxxxxxxxx] > Sent: Thursday, February 18, 2010 8:23 PM > To: Rajat Jain > Cc: linux-hotplug@xxxxxxxxxxxxxxx; linux-pci@xxxxxxxxxxxxxxx > Subject: Re: How does Linux handle PCI-E Surprise unplug? > > On Thu, Feb 18, 2010 at 11:35:33AM +0530, Rajat Jain wrote: > > Hi, > > > > I'm keen to understand how the Linux kernel handles surprise removal of > > a device, from a PCI-e slot that supports "Hot-plug Surprise" removal > > (in slot capabilities). > > > > Consider that the device in the slot is working normally, with its > > driver attached to the device, and is doing all sorts of read / write > > operations on the device registers that have been mapped into the PCI > > memory space. Now when that device is suddenly plugged out (and thus its > > registers suddenly disappear from the PCI memory space), the device > > driver is still unaware as it is doing the register reads / writes on > > the device. At this point, IMHO any attempt to access the device > > registers will result in an exception (BUS error?) as the device is > > gone. Correct? > > The driver will suddenly start reading all 0xff and will then need to > abort whatever it was doing. Usually all drivers handle this just fine > today, as this is what they needed to do when they were pccard devices. > Nothing new here at all. > Does that mean accessing PCI memory mapped registers for a non-existent device has effects that are localized ONLY to the driver of that device? In other words, kernel does not notice or does not even become AWARE that a driver is trying to access non-existent memory mapped registers? So trying to access a HW that does not exist is totally legal in that sense? Is HW NOT supposed to generate an error in this case - as far as I had read, any access to non existent physical addresses should result in a bus error ... no? Thanks, Rajat Jain -- 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
