Re: [PATCH 10/12] platform/early: implement support for early platform drivers

[Bartosz Golaszewski <brgl@bgdev.pl>]

2018-05-14 15:37 GMT+02:00 Rob Herring <robh+dt@kernel.org>:
> On Fri, May 11, 2018 at 11:20 AM, Bartosz Golaszewski <brgl@bgdev.pl> wrote:
>> From: Bartosz Golaszewski <bgolaszewski@baylibre.com>
>>
>> This introduces the core part of support for early platform drivers
>> and devices.
>>
>
> It looks like most of your prep patches are to separate the alloc and
> init of platform devices because you are essentially making early
> devices/drivers a sub-class. Maybe you could avoid doing that and
> simplify things a bit. Comments below based on doing that...
>

My aim was to change as little as possible for everybody else while
fixing our problem. These changes are already controversial enough
without risky reusing of existing fields in common structures. I was
just afraid that there are too many intricacies for it to be safe.

>> +/**
>> + * struct early_platform_driver
>> + *
>> + * @pdrv: real platform driver associated with this early platform driver
>> + * @list: list head for the list of early platform drivers
>> + * @early_probe: early probe callback
>> + */
>> +struct early_platform_driver {
>> +       struct platform_driver pdrv;
>> +       struct list_head list;
>
> Couldn't you use an existing list in driver_private until you move
> over to the normal bus infra.
>

This is something that the previous implementation did. It was quite
unreadable, so I decided to go with a separate list.

>> +       int (*early_probe)(struct platform_device *);
>
> Just add this to platform_driver.
>

This would extend the structure for everybody else while there'll be
very few such devices and not all systems would even require it.

>> +};
>> +
>> +/**
>> + * struct early_platform_device
>> + *
>> + * @pdev: real platform device associated with this early platform device
>> + * @list: list head for the list of early platform devices
>> + * @deferred: true if this device's early probe was deferred
>> + * @deferred_drv: early platform driver with which this device was matched
>> + */
>> +struct early_platform_device {
>> +       struct platform_device pdev;
>> +       struct list_head list;
>
> Use a list in device_private?
>
>> +       bool deferred;
>> +       struct early_platform_driver *deferred_drv;
>
> Can't you use the existing deferred probe list?
>

I thought about it, but I was afraid there could be some timing issues
with that and decided against it. The early deferral also doesn't work
in a workque, but is synchronous instead.

Best regards,
Bartosz Golaszewski