multiple drivers for same hardware

multiple drivers for same hardware

[Kumar Gala]

We have some scenarios in which we might have 2 different drivers (one in kernel or one user space as an example) and wanted to see how we'd convey in the device tree which driver should "claim" the specific device instance.

>From glancing at the OF specs it seems we could utilize the precedence order of compatible as a means to specify.  So something like:

[ bind with UIO instead of standard driver ]

	compatible = "gianfar-lnx-uio", "gianfar";

vs [ bind with stock kernel driver ]
	compatible = "gianfar";

The other thought I had was introducing a new property like:

	linux-drv = "gianfar-uio";
	compatible = "gianfar";

thoughts?

- k

Re: multiple drivers for same hardware

[Mitch Bradley]

On 1/13/2012 8:52 AM, Kumar Gala wrote:
> We have some scenarios in which we might have 2 different drivers (one in kernel or one user space as an example) and wanted to see how we'd convey in the device tree which driver should "claim" the specific device instance.
>
>  From glancing at the OF specs it seems we could utilize the precedence order of compatible as a means to specify.  So something like:
>
> [ bind with UIO instead of standard driver ]
>
> 	compatible = "gianfar-lnx-uio", "gianfar";
>
> vs [ bind with stock kernel driver ]
> 	compatible = "gianfar";


That is certainly the standard way of doing it.

>
> The other thought I had was introducing a new property like:
>
> 	linux-drv = "gianfar-uio";
> 	compatible = "gianfar";
>
> thoughts?

Why add a new mechanism when there is an existing one that does what you 
want?



>
> - k
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>

Re: multiple drivers for same hardware

[Stuart Yoder]

On Fri, Jan 13, 2012 at 12:52 PM, Kumar Gala <galak-XVmvHMARGAS8U2dJNN8I7kB+6BGkLq7r@public.gmane.org> wrote:
> We have some scenarios in which we might have 2 different drivers (one in kernel or one user space as an example) and wanted to see how we'd convey in the device tree which driver should "claim" the specific device instance.
>

I don't think we want to use the device tree for this, as this is
really configuration information.

The vfio user space driver model should solve this when it is implemented.

The basic approach with vfio will be something like:
    -a new kernel argument specifies a list of devices that the kernel
should leave alone and not bind to
    -in user space, you bind desired devices to vfio through sysfs
    -the vfio subsystem makes the bound devices available through /dev/vfio
    -user space can then mmap the devices, hook their interrupts, do
     iommu config,etc through file description operations

Stuart