On 2017-08-10 18:30, Jason Gunthorpe wrote:
On Thu, Aug 10, 2017 at 12:18:11PM +0200, Michal Suchánek wrote:


> Existing bus implementations do properly chain to driver shutdown (eg
> look at mmc_bus_shutdown) and it appears to have been written like

Neither isa nor ibmebus does. These are two random buses I tried to
look at.

I'm not following, I see this:

static void ibmebus_bus_device_shutdown(struct device *dev)
{
        struct platform_device *of_dev = to_platform_device(dev);
        struct platform_driver *drv = to_platform_driver(dev->driver);

        if (dev->driver && drv->shutdown)
                drv->shutdown(of_dev);
}

It looks to me like in this case the struct device_driver shutdown is
not used, and instead the struct platform_driver shutdown is called.

And it is not used even if a device driver sets it and expects it to run.


> this so that the bus can insert code before and after calling the
> driver shutdown.

So basically there is bus pre-shutdown and post-shutdown hook jumbled
together in one function.

and a redirect, apparently.

While I can understand the concept of post-shutdown hook I wonder
what gross hack would require a pre-shutdown hook.

TPM requires pre-shutdown.

Yes, a class pre-shutdown. Not a bus pre-shutdown, however.

I have no idea what business has a bus driver before a device shuts down.


The Linux development process at its best. There is poor design
implemented so when touching the code it is extended to worse because

I'm not sure I completely agree, there is obviously a lot going on with
bus->shutdown.

If you want to go ahead with your patch then please also rename the
class shutdown to shutdown_pre to make it clear it is doing something
different.

That makes sense.

Thanks

Michal

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