linux-kernel - Re: [PATCH] ACPI: Add _DEP(Operation Region Dependencies) support to fix battery issue on the Asus T100TA

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Date:	Wed, 19 Nov 2014 17:05:47 +0100
From:	Wolfram Sang <wsa@...-dreams.de>
To:	Lan Tianyu <tianyu.lan@...el.com>
Cc:	rjw@...ysocki.net, lenb@...nel.org, robert.moore@...el.com,
	lv.zheng@...el.com, shigorin@...il.com, adamw@...pyassassin.net,
	jan.brummer@...os.org, linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org,
	devel@...ica.org
Subject: Re: [PATCH] ACPI: Add _DEP(Operation Region Dependencies) support to
 fix battery issue on the Asus T100TA

On Wed, Nov 19, 2014 at 11:20:41PM +0800, Lan Tianyu wrote:
> ACPI 5.0 introduces _DEP to designate device objects that OSPM should
> assign a higher priority in start ordering due to future operation region
> accesses.
> 
> On Asus T100TA, ACPI battery info are read from a I2C slave device via
> I2C operation region. Before I2C operation region handler is installed,
> battery _STA always returns 0. There is a _DEP method of designating
> start order under battery device node.
> 
> This patch is to implement _DEP feature to fix battery issue on the Asus T100TA.
> Introducing acpi_dep_list and adding dep_unmet count in the struct
> acpi_device. During ACPI namespace scan, create struct acpi_dep_data for a
> valid pair of master (device pointed to by _DEP)/slave(device with _DEP), record
> master's and slave's ACPI handle in it and put it into acpi_dep_list. The dep_unmet
> count will increase by one if there is a device under its _DEP. Driver's probe() should
> return EPROBE_DEFER when find dep_unmet larger than 0. When I2C operation
> region handler is installed, remove all struct acpi_dep_data on the acpi_dep_list
> whose master is pointed to I2C host controller and decrease slave's dep_unmet.
> When dep_unmet decreases to 0, all _DEP conditions are met and then do acpi_bus_attach()
> for the device in order to resolve battery _STA issue on the Asus T100TA.
> 
> Reference: https://bugzilla.kernel.org/show_bug.cgi?id=69011 
> Tested-by: Jan-Michael Brummer <jan.brummer@...os.org>
> Tested-by: Adam Williamson <adamw@...pyassassin.net>
> Tested-by: Michael Shigorin <shigorin@...il.com>
> Signed-off-by: Lan Tianyu <tianyu.lan@...el.com>

As long as the I2C related changes are that minimal:

Acked-by: Wolfram Sang <wsa@...-dreams.de> for the I2C part


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