[RFC] drm: implement generic firmware eviction

[David Herrmann]

Hi

On Fri, Aug 26, 2016 at 9:57 AM, Hans de Goede <hdegoede at redhat.com> wrote:
> Hi,
>
> On 26-08-16 02:00, David Herrmann wrote:
>>
>> Provide a generic DRM helper that evicts all conflicting firmware
>> framebuffers, devices, and drivers. The new helper is called
>> drm_evict_firmware(), and takes a flagset controlling which firmware to
>> kick out.
>>
>> This is meant to be used by drivers in their ->probe() callbacks of their
>> parent bus, before calling into drm_dev_register().
>>
>> Signed-off-by: David Herrmann <dh.herrmann at gmail.com>
>> ---
>> Hey
>>
>> This is just compile-tested for now. I just want to get some comments on
>> the
>> design. I decided to drop the sysfb infrastructure and rather just use
>> this
>> generic helper. It keeps things simple and should work just fine for all
>> reasonable use-cases.
>>
>> This will work with SimpleDRM out-of-the-box on x86.
>>
>> Architectures with dynamic simple-framebuffer devices are not supported
>> yet. I
>> actually have no idea what the strategy there is? Can the DeviceTree
>> people come
>> up with something? Am I supposed to call of_platform_depopulate()? Or
>> of_detach_node()? Or what?
>
>
> I'm not sure we would want to remove the device at all, we certainly should
> not
> be removing the dt_node from the devicetree IMHO. Having that around to see
> how
> the bootloader set things up is really useful for debugging and normally we
> should never modify the devicetree as set up by the bootloader.
>
> Why not just unbind the driver from the platform device? That should be
> enough.

That will leave IORESOURCE_MEM around, causing conflicts if
re-used/claimed by other devices/drivers. Furthermore, it is really
fragile leaving the device around, without any control over possible
future driver probing.

Thanks
David