Hi Arnd,
On 10/16/2015 03:26 PM, Arnd Bergmann wrote:
> On Friday 16 October 2015 15:06:45 Eric Auger wrote:
>
>> I've since forgotten his answer, but the fact that
>>> __symbol_get() is only defined for modules makes it moot, we either need
>>> to make symbol_get() work or define __symbol_get() for non-module
>>> builds.
>> I currently don't see any solution for any of those. The only solution I
>> can see is someone registers the reset function pointer to vfio.
>>
>> I think we could keep the existing reset modules, do the request_module
>> from VFIO, using their module name registered in the lookup table. But
>> instead of having the reset function in the look-up table we would have
>> the reset modules register their reset function pointer to VFIO. I think
>> this could work around the symbol_get issue.
>>
>> This still leaves the layer violation argument though.
>>
>> Assuming this works, would that be an acceptable solution, although I
>> acknowledge this does not perfectly fit into the driver model?
>
> I think it's possible to avoid the layering violation that way too,
> by loading the module based on the compatible string, with a module_alias.
>
> static void vfio_platform_get_reset(struct vfio_platform_device *vdev,
> struct device *dev)
> {
> const char *compat;
> int (*reset)(struct vfio_platform_device *);
> int ret, i;
> char modname[256];
>
> ret = device_property_read_string(dev, "compatible", &compat);
> if (ret)
> return;
>
> reset = vfio_platform_lookup_reset(compat);
> if (!reset) {
> snprintf(modname, "vfio-reset:%s", compat);
> request_module(modname);
> reset = vfio_platform_lookup_reset(compat);
> }
>
> vdev->reset = reset;
> }
>
> ---
>
> #define module_vfio_reset_handler(compat, reset) \
> MODULE_ALIAS("vfio_reset" compat); \
> static int reset ## _module_init(void) \
> { \
> return vfio_reset_register(THIS_MODULE, compat, &reset); \
> }
>
> I think that solution is good enough, as it avoids most of the
> problems with the current implementation but is a simple enough change.
That looks a good perspective. Thanks for the hint! Let's code now ;-)
Best Regards
Eric
>
> Arnd
>
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