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

[Wolfram Sang]

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@xxxxxxxxx>
> Tested-by: Adam Williamson <adamw@xxxxxxxxxxxxxxxxx>
> Tested-by: Michael Shigorin <shigorin@xxxxxxxxx>
> Signed-off-by: Lan Tianyu <tianyu.lan@xxxxxxxxx>

As long as the I2C related changes are that minimal:

Acked-by: Wolfram Sang <wsa@xxxxxxxxxxxxx> for the I2C part

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