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    SubjectRe: [PATCH 1/2] cs5535-gpio: add AMD CS5535/CS5536 GPIO driver support
    On Thu, 11 Jun 2009 23:35:55 +0200
    Tobias Müller <Tobias_Mueller@twam.info> wrote:

    > >> /**
    > >> * Some GPIO pins
    > >> *  31-29,23 : reserved (always mask out)
    > >> *  28       : Power Button
    > >> *  26       : PME#
    > >> *  22-16    : LPC
    > >> *  14,15    : SMBus
    > >> *  9,8      : UART1
    > >> *  7        : PCI INTB
    > >> *  3,4      : UART2/DDC
    > >> *  2        : IDE_IRQ0
    > >> *  1        : AC_BEEP
    > >> *  0        : PCI INTA
    > >> *
    > >> * If a mask was not specified, be conservative and only allow:
    > >> *  1,2,5,6,10-13,24,25,27
    > >> */
    > >>
    > >> I'll add this in my patch to clear it out.
    > >>
    > >
    > > But why are you being conservative in the first place?  If
    > > something's using GPIOs, unless they're unmapped, you should allow
    > > it to use them without requiring a boot arg.
    > >
    > > For example, OLPC uses GPIO 7 for its DCON IRQ.  With the masking
    > > scheme, OLPC will need to set that mask from the default.  I don't
    > > see the point of having the mask at all if other drivers in the
    > > kernel are going to be requesting GPIOs (presumably they know what
    > > they're doing).
    > Hmm... OK, this makes sense. So default mask allow everything exept
    > reserved pins and pin 28 (power button).
    >
    > I think the mask is quite useful if you've critical things on GPIO
    > pins and they should be changeable (especially from userspace and when
    > non-root users are allowed to use userspace gpio).

    I agree that it would be useful for userspace, just not for
    kernelspace. Is there a way that you can have it only enforce the
    mask if the request is coming from userspace?
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