linux-kernel - Re: [PATCH] gpiolib-acpi: introduce acpi_get_gpio_by

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Thu, 4 Apr 2013 11:42:11 +0200
From:	Benjamin Tissoires <benjamin.tissoires@...il.com>
To:	Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:	linux-kernel@...r.kernel.org,
	Grant Likely <grant.likely@...retlab.ca>,
	Linus Walleij <linus.walleij@...aro.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Mathias Nyman <mathias.nyman@...ux.intel.com>,
	linux-acpi@...r.kernel.org
Subject: Re: [PATCH] gpiolib-acpi: introduce acpi_get_gpio_by_index() helper

On Thu, Apr 4, 2013 at 11:38 AM, Mika Westerberg
<mika.westerberg@...ux.intel.com> wrote:
> On Thu, Apr 04, 2013 at 11:19:53AM +0200, Benjamin Tissoires wrote:
>> Hi Mika,
>>
>> On Wed, Apr 3, 2013 at 12:56 PM, Mika Westerberg
>> <mika.westerberg@...ux.intel.com> wrote:
>> > Instead of open-coding ACPI GPIO resource lookup in each driver, we provide
>> > a helper function analogous to Device Tree version that allows drivers to
>> > specify which GPIO resource they are interested (using an index to the GPIO
>> > resources). The function then finds out the correct resource, translates
>> > the ACPI GPIO number to the corresponding Linux GPIO number and returns
>> > that.
>> >
>> > Signed-off-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
>> > ---
>> >  Documentation/acpi/enumeration.txt |   32 ++++++++++++++-
>> >  drivers/gpio/gpiolib-acpi.c        |   77 ++++++++++++++++++++++++++++++++++++
>> >  include/linux/acpi_gpio.h          |   17 ++++++++
>> >  3 files changed, 125 insertions(+), 1 deletion(-)
>> >
>> > diff --git a/Documentation/acpi/enumeration.txt b/Documentation/acpi/enumeration.txt
>> > index 94a6561..b0d5410 100644
>> > --- a/Documentation/acpi/enumeration.txt
>> > +++ b/Documentation/acpi/enumeration.txt
>> > @@ -199,6 +199,8 @@ the device to the driver. For example:
>> >         {
>> >                 Name (SBUF, ResourceTemplate()
>> >                 {
>> > +                       ...
>> > +                       // Used to power on/off the device
>> >                         GpioIo (Exclusive, PullDefault, 0x0000, 0x0000,
>> >                                 IoRestrictionOutputOnly, "\\_SB.PCI0.GPI0",
>> >                                 0x00, ResourceConsumer,,)
>> > @@ -206,10 +208,20 @@ the device to the driver. For example:
>> >                                 // Pin List
>> >                                 0x0055
>> >                         }
>> > +
>> > +                       // Interrupt for the device
>> > +                       GpioInt (Edge, ActiveHigh, ExclusiveAndWake, PullNone,
>> > +                                0x0000, "\\_SB.PCI0.GPI0", 0x00, ResourceConsumer,,)
>>
>> Sorry for coming late in the GPIO ACPI discussion, but when I see this
>> documentation, I wonder:
>> wouldn't it be feasible to find the correct GPIO by its type? Here, we
>> have a GpioIo and a GpioInt, and I bet this would be sometime more
>> useful to request the first GpioInt without knowing the correct order
>> of declarations.
>
> Why not. But then again you can always check the type returned in the
> acpi_gpio_info structure and pick the first GpioInt (if you have multiple
> GPIO resources).
>
>> It may be feasible by walking the tree, but a helper would be of great
>> help (thinking at i2c-hid here, which can not rely on indexes in the
>> DSDT).
>
> Well, index is the only thing we can rely on unfortunately. There's nothing
> like names or anything like that.
>
> What I've seen from ACPI enumerated i2c-hid devices there is only one GPIO
> resource (GpioInt) declared.

Ok, thanks for the answer. I guess the idea would be to pick the index
0, check the type, and try indexes 1 or 2 if it's not GpioInt. I bet
there will be devices with more than one Gpio as most of I2C input
device have a reset line (except if Microsoft forces them not to have
one).

Cheers,
Benjamin
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/