driver_attach question

driver_attach question

[Anil kumar]

Hi,

Should driver_attach( ) return an error value?

I have disabled a device in the system bios, The
driver fails to report -ENODEV.
This is for 2.6.11.1 kernel
When I dig through the PCI subsystem and driver_attach
code, I find that :

pci_register_driver is returing zero(no error) even
when the device is not present in the system. 
But when I check driver_attach( ), I get -ENODEV for
driver_probe_device(). which is correct. But
driver_attach( ) does not return this error value. 
driver attach( ) is called in bus_add_driver( ) and
bus_add_driver just returns error=0
Hence I get error=0 in pci_register_driver.

Am I missing something in the flow?

int pci_register_driver( )
{
.....
.....
error = driver_register(&drv->driver);
return error;
}

int driver_register(struct device_driver * drv)
{
.....
return bus_add_driver(drv);
}

int bus_add_driver(struct device_driver * drv)
{
.....
driver_attach(drv);
...
return error;
}

void driver_attach(struct device_driver * drv)
{
....
error = driver_probe_device(drv, dev);
....
}

with regards,
  Anil




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Re: driver_attach question

[Adam Belay]

On Tue, Dec 13, 2005 at 06:07:54PM -0800, Anil kumar wrote:
> Hi,
> 
> Should driver_attach( ) return an error value?
> 
> I have disabled a device in the system bios, The
> driver fails to report -ENODEV.
> This is for 2.6.11.1 kernel
> When I dig through the PCI subsystem and driver_attach
> code, I find that :
> 
> pci_register_driver is returing zero(no error) even
> when the device is not present in the system. 
> But when I check driver_attach( ), I get -ENODEV for
> driver_probe_device(). which is correct. But
> driver_attach( ) does not return this error value. 
> driver attach( ) is called in bus_add_driver( ) and
> bus_add_driver just returns error=0
> Hence I get error=0 in pci_register_driver.
> 
> Am I missing something in the flow?

The basic strategy is to leave the driver loaded so that
later, if the a device is hotplugged or the user adds a
dynamic id to an existing device, it will be available.
In other words, even if the registration of a driver does
not result in device detection, the operation can still
considered successful.

Does this answer your question?

Thanks,
Adam