linux-kernel - RE: How to populate Battery information through ACPI tables

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Date:	Tue, 19 Feb 2013 18:22:01 +0000
From:	"Pallala, Ramakrishna" <ramakrishna.pallala@...el.com>
To:	"Westerberg, Mika" <mika.westerberg@...el.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Zhang, Rui" <rui.zhang@...el.com>
Subject: RE: How to populate Battery information through ACPI tables

> > > > > > I am trying to populate battery related information through
> > > > > > ACPI tables and do battery management through non acpi
> > > > > > drivers.  Can you tell or point me on how to populate the ACPI
> > > > > > tables in FW/BIOS and get them in OS? I am new to ACPI world.
> > > > >
> > > > > You should start by reading Documentation/acpi/enumeration.txt.
> > > > >
> > > > > Also can you describe with bit more details, what you are trying
> > > > > to do? A new battery driver that is enumerated from ACPI namespace,
> perhaps?
> > > > >
> > > > > Do you have a DSDT table in hand which we could take a peek?
> > > >
> > > > Thanks Mika for the pointers. I have looked at the documentation.
> > > >
> > > > we already have i2c driver for battery monitoring but the chip
> > > > needs initialized with characterization data. We wanted to
> > > > populate/pass this data through ACPI table to the i2c slave driver.
> > > >
> > > > How can I do that? Can I pass characterization data through ACPI
> > > > table to the i2c slave device?
> > >
> > > Is the characterization data available in DSDT (or SSDT) table? If
> > > yes, then you can just use the fact that
> > > ACPI_HANDLE(&i2c_client->dev) returns a valid ACPI handle for your
> > > device. You can use this handle to call some ACPI method or whaterver is
> needed to extract that information.
> >
> > As of now this data is not there in any table. I want to put this data in DSDT
> table.
> > The data I want to put is specific to the device  and will be around 1K bytes.
> >
> > One question, How the table and device are linked? Is it by device name/id?
> 
> In principle, yes. We create devices based on the IDs on the DSDT table.
> 
> > Next, how to put this characterization data into the DSDT table?
> 
> Typically this is done by BIOS team but you can experiment yourself just by
> taking an existing DSDT, disassembling it with iasl, do the changes and
> reassembling it again. You can then include this with your kernel or initrd image.
> 
> I have no idea how that data is supposed to look like or be represented in the
> DSDT.
> 
> You should also familiarize yourself with ACPI by reading the ACPI 5.0 spec from
> acpi.info.

Mika, I want to populate this characterization data as device specific/custom data which could be anything
And may not be entirely related to battery. Is this is possible?

I will also go through the spec but this info would help me to resolve some initial hurdles in my work.

Note: I am not going to use ACPI based battery monitoring but I need this data from acpi tables.

Thanks,
Ram
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