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SubjectRe: [RFCLUE2] 64 bit driver 32 bit app ioctl
William D Waddington writes:
> Apologies for dashing this off without the proper homework. My
> customer is out of country doing an installation, and didn't test
> this configuration first :(
>
> Customer is running RHEL3 on a 64 bit PC. Running the 64 bit kernel
> and my 64 bit driver. They are calling the driver from their 32 bit
> app. The driver supports a whole mess of ioctls.
>
> It seems that the kernel is trapping the 32-bit ioctl call and returning
> an error to the app w/out calling the driver. It looks like
> register_ioctl32_conversion() can convice the kernel that the driver can
> handle 32-bit calls, but it has to be called for each ioctl cmd (??)

In these old pre-compat_ioctl kernels you have to register each
ioctl command individually. Yes that sucks. Live with it.

> Putting aside (please) discussion of whether the kernel should presume
> to hijack private ioctls, and whether I should be using the ioctl
> interface at all (compatibility with app interface going back to 2.0
> and SunOS) is there some way to make _one_ register call to indicate
> that all my cmds are safe, or maybe an alternate ioctl entry point
> that the kernel won't trap?

Not as long as you're stuck with old 2.4 kernels. 2.6 kernels since
2.6.11-rc2 allow you to set up a single ->compat_ioctl() method,
but not even RHEL4 has that yet.
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