Re: [Swsusp-devel] Re: Dropping CONFIG_PM_DISK?

["Michael Frank" <mhf@linuxmail.org>]

On Mon, 01 Mar 2004 22:39:52 +1100, Benjamin Herrenschmidt <benh@kernel.crashing.org> wrote:

>
>> >> - that 2.4 style PM got depreciated and let die before the
>> >>    "new-driver-model" PM is workin
>> >
>> > Except that it never worked
>>
>> It is actively used for ide, network, serial drivers with swsusp2.
>
> Without any proper ordering guarantee, IDE could take requests
> after beeing suspended, which could be fatal (and cause data loss)
> etc...

Appreciated, suspending a driver like sending XOFF to a tty is ideal,
but not neccessary for _most_ drivers (software suspend) purpose.

Wrt IDE, in practice all processes get frozen well before
suspending drivers. Tested and no issues were ever reported with 2.4.

>
> Moving to the new model is easy. I don't see why we should have had
> such a "compatibility" path on a major kernel version, that makes
> no sense, just help fixing the drivers that need more fixing instead.

What for write new drivers for (fast obsoleting) hardware?.

- Developer time is the most precious resource
- Testing of drivers is in practice very difficult due to lack of
     several variations of HW (one can't really test anything in one box)
- It will take _years_ for drivers to become available and reach the
   stability of 2.4 drivers.
- Many drivers will die for lack of overall resources to port them.

So, why burn resources on reinventing wheels, which end up poorly
tested and run like a disk sliced of a tree...

What is needed is a  _compatible_ infrastructure to _any_ 2.4 driver
in existence and also provideing rudimentary centralized suspend and
resume capability.

This infrastructure could even be a config option
	CONFIG_24_DRIVER_SUPPORT
and be independent of the new model.

Then one could just drop in a driver from 2.4 and use it.

People having time to make new "pretty" drivers could
also use this facility for cross checking.

>
>> >
>> >> - that perfectly good drivers were rewritten from scratch,
>> >>    but without functioning PM support
>> >
>> > Please, give names.
>> >
>>
>> A few I tested:
>>
>> AGP (sis, savage)
>> trident (Ali153x)
>> Serial (82x50)
>> Yenta (Toshiba Topic95)
>>
>> Regards
>> Michael