On 07/17/2014 12:26 AM, Alexandre Courbot wrote:
On Thu, Jul 17, 2014 at 3:37 PM, Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
On 07/16/2014 11:09 PM, Alexandre Courbot wrote:
On Thu, Jul 17, 2014 at 8:11 AM, Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
The gpio include file and the gpio documentation declare and document
GPIOF_ACTIVE_LOW as one of the flags to be passed to gpio_request_one
and related functions. However, the flag is not evaluated or used.
Check the flag in gpio_request_one and set the gpio internal flag
FLAG_ACTIVE_LOW if it is set.
What is the point since the integer GPIO API has no clue of the
active-low status of a GPIO? It is only used by the gpiod and sysfs
interfaces.
One can use gpio_request_one() to export a gpio pin to user space from
the kernel. That code path does use the flag, as you point out yourself
above.
Ok, in that case I suppose it makes sense.
Reviewed-by: Alexandre Courbot <acourbot@xxxxxxxxxx>
One could also argue that the integer gpio API _should_ support this as
well,
but that is a different question.
Probably not going to happen. The integer GPIO interface is deprecated
and users who need new features should seriously consider switching to
gpiod.
The new API is unfortunately not equivalent to the old one. For example,
if I understand correctly, gpiod_get is expected to be used instead of
gpio_request_one. That may work nicely in a world with full DT or ACPI
support, but doesn't work as well otherwise unless one drops the notion
of using platform specific drivers built as modules (gpiod_add_lookup_table
is not exported, and there is no remove function).
Specifically, I don't see an easy way to convert mdio-gpio to use the new
model, and that driver could really use support for an API which supports
active-low pins. And even if gpiod_add_lookup_table was supported,
converting a driver like this would be a major pain. Sure, it would be
all easy if there would be a gpiod equivalent to gpio_request_one and
gpio_request_array, but that is not the case. This makes converting
drivers from the old to the new model challenging enough that I suspect
that it won't really happen.
Guenter
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