RE: [PATCH V7 5/7] ACPI: Delay the enumeration on the devices whose dependency has not met

[Gabriele Paoloni]

Hi Rafael

Many thanks for your review

> -----Original Message-----
> From: Rafael J. Wysocki [mailto:rjw@xxxxxxxxxxxxx]
> Sent: 13 March 2017 21:25
> To: Yuanzhichang
> Cc: catalin.marinas@xxxxxxx; will.deacon@xxxxxxx; robh+dt@xxxxxxxxxx;
> frowand.list@xxxxxxxxx; bhelgaas@xxxxxxxxxx; rafael@xxxxxxxxxx;
> mark.rutland@xxxxxxx; arnd@xxxxxxxx; linux-arm-
> kernel@xxxxxxxxxxxxxxxxxxx; linux-acpi@xxxxxxxxxxxxxxx;
> lorenzo.pieralisi@xxxxxxx; benh@xxxxxxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; Linuxarm; devicetree@xxxxxxxxxxxxxxx; linux-
> pci@xxxxxxxxxxxxxxx; linux-serial@xxxxxxxxxxxxxxx; minyard@xxxxxxx;
> liviu.dudau@xxxxxxx; zourongrong@xxxxxxxxx; John Garry; Gabriele
> Paoloni; zhichang.yuan02@xxxxxxxxx; kantyzc@xxxxxxx; xuwei (O)
> Subject: Re: [PATCH V7 5/7] ACPI: Delay the enumeration on the devices
> whose dependency has not met
> 
> On Monday, March 13, 2017 10:42:41 AM zhichang.yuan wrote:
> > In commit 40e7fcb1929(ACPI: Add _DEP support to fix battery issue on
> Asus
> > T100TA), the '_DEP' was supported to solve the dependency of Asus
> battery. But
> > this patch is specific to Asus battery device.
> > In the real world, there are other devices which need the dependency
> to play the
> > role on the enumeration order. For example, all the Hip06 LPC
> > periperals(IPMI-BT, uart, etc) must be scanned after the LPC host
> driver
> > finished the probing. So, it makes sense to add a checking whether
> the ACPI
> > device meet all the dependencies during its enumeration slot, if not,
> the
> > enumeration will be delayed till all dependency master finish their
> work.
> >
> > This patch adds the dependency checking in ACPI enumeration, also the
> > corresponding handling to retrigger the Hip06 LPC peripherals'
> scanning.
> 
> AFAICS, _DEP is generally abused in the wild and cannot be made
> generic.  Sorry.

Another option here would be to revert this patch and add a dependency
check in the probe functions of the LPC possible children nodes (e.g. 
in the IPMI driver:
http://elixir.free-electrons.com/source/drivers/char/ipmi/ipmi_si_intf.c?v=4.10#L2683
)  

we could add 

	if (device->dep_unmet)
		return -EPROBE_DEFER;

as we now have in acpi/battery.c...

I think this should not make any difference for current shipped FW that has
got no DEP method...

What do you think?

Many Thanks
Gab

> 
> Thanks,
> Rafael