Hi Rafael

Many thanks for your review

-----Original Message-----
From: Rafael J. Wysocki [mailto:rjw@rjwysocki.net]
Sent: 13 March 2017 21:25
To: Yuanzhichang
Cc: catalin.marinas@arm.com; will.deacon@arm.com; robh+dt@kernel.org;
frowand.list@gmail.com; bhelgaas@google.com; rafael@kernel.org;
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kernel@lists.infradead.org; linux-acpi@vger.kernel.org;
lorenzo.pieralisi@arm.com; benh@kernel.crashing.org; linux-
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pci@vger.kernel.org; linux-serial@vger.kernel.org; minyard@acm.org;
liviu.dudau@arm.com; zourongrong@gmail.com; John Garry; Gabriele
Paoloni; zhichang.yuan02@gmail.com; kantyzc@163.com; 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:

quoted

In commit 40e7fcb1929(ACPI: Add _DEP support to fix battery issue on

Asus

quoted

T100TA), the '_DEP' was supported to solve the dependency of Asus

battery. But

quoted

this patch is specific to Asus battery device.
In the real world, there are other devices which need the dependency

to play the

quoted

role on the enumeration order. For example, all the Hip06 LPC
periperals(IPMI-BT, uart, etc) must be scanned after the LPC host

driver

quoted

finished the probing. So, it makes sense to add a checking whether

the ACPI

quoted

device meet all the dependencies during its enumeration slot, if not,

the

quoted

enumeration will be delayed till all dependency master finish their

work.

quoted

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