How the kernel scan the pci devices:
In /arch/x86/pci/legacy.c,
*pci_legacy_init()* invoke
- *pcibios_scan_root(0) *to scan pci devices from the root bus,
if the bus is already scanned then just return;
else the
- *pci_scan_bus_parented() *will be invoked, in this function the
* *-* pci_create_bus()* will create pci_bus for the
corresponding bus and add it to the *pci_root_buses*.
- *pci_scan_child_bus() *is* *invoked to enumerate all the
devices of that bus. for each device number(each bus host
up to 32 devices, see *Page 303, LDD3*) invoke
- *pci_scan_slot() *to scan its 8 function number, here
the
- *pci_scan_single_device()* be invoked, that means
for each device the
- *pci_scan_device() *will be invoked, if the
device
exist, the
- *pci_device_add() *will add the device to the
devices list
of the bus it belongs to.
Oh, A lot of code to read, I think you will be interest in
the *pci_scan_device()* function, this function gets
*configuration registers* of the pci device(*Page 308, LDD3*)
eh, I must go to class now...
On Tue, Nov 30, 2010 at 4:56 AM, Bond <[email protected]> wrote:
> On Tue, Nov 23, 2010 at 3:07 AM, Yuchen Liao <[email protected]> wrote:
> > AFAIK, in the device_add() function (in driver/base/core.c), kernel will
> > invoke "device_create_file()" function to create the "uevent" file;
> > (The kobj is also added in this device_add() function by invoke
> > kobject_add() function)
> > In user space, the udevd is listening the NETLINK_KOBJECT_EVENT to get
> the
> > "uevent" event. Then it will find a match udev rule under the
> > /etc/udev/rules.d/. It will make changes according to the rule(Like
> create
> > the device file under /dev).
> > Every device when it is register, it will create a uevent file(by this
> way,
> > can trigger a hotplug event), can write a "add" or "remove" command to
> add
> > or remove a device.
> > When starting computer, kernel will register a lot of devices, but the
> > udev(in user space) is not start. After it start, it will scan the sysfs,
> to
> > get all the uevent file, and write "add" into it. In this way, the event
> > been triggered.
> > ----
> > I'm not so sure that I'm right. Please correct me if there is anything
> > wrong. Thank you~
> Hi thanks your explanation was very good.
> I have been doing some research on this aspect and replying you after
> so many days it is helpful.
> What I came across was some thing known as pci-core for PCI devices
> and USB core for USB devices.
> So that is one thing I surely want to understand.
> My objective by this exercise is to be able to write a kernel which is
> working on bare metal.(I just want a small set of code which can work)
> So I want to understand it more.If some one has more thoughts here
> then share it please.
>
--
from Yuchen Liao via Gmail
yyloves.me
