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    SubjectRe: [linux-pm] [PATCH 2/9] PM: suspend_block: Add driver to access suspend blockers from user-space
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    On Tuesday 27 April 2010, Alan Stern wrote:
    > On Mon, 26 Apr 2010, Arve Hjønnevåg wrote:
    >
    > > > If you insist on using ioctl for init, you should use the standard
    > > > convention for passing variable-length data. The userspace program
    > > > sets up a fixed-size buffer containing a pointer to the name and the
    > > > name's length, and it passes the buffer's address as the ioctl
    > > > argument.
    > >
    > > Are you sure that is the standard? I searched for ioctls with NAME in
    > > their name and only found one that passed the name that way. The rest
    > > used fixed length string buffers, or passed the buffersize to _IOC
    > > like I do. For instance, input.h has ioctls to read string and
    > > bitmasks where user space specify the buffer size as an argument to
    > > the ioctl macro. These pass data from the kernel to user space, but I
    > > don't passing a string length is any worse than passing a buffer size.
    >
    > You're right. Okay, I withdraw my objection.

    In the meantime, though, I thought that the suspend blocker might be created
    by _open() if we found a way to automatically choose a name for it. That'd be
    kind of logical, since it's later destroyed by _release().

    So, what about using the name of the process that opened the special device
    file (or that name with'0' appended, or generally with a number appended) as
    the suspend blocker name?

    Rafael
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