RE: ioctls, etc. (was Re: [PATCH 1/4] sas: add flag for locally attached PHYs)

[Bagalkote, Sreenivas]

>Jeff Garzik wrote:
>> Do you know where there are some clear guidelines on the use of 
>> pointers in a structure passed to an ioctl to lessen (or bypass) 
>> 32<->64 compat ioctl thunking?
>
>Its impossible.  If you pass pointers, you need to thunk.  
>(Not even passing pointers via sysfs can avoid this.)  
>Consider running a 32-bit app (with 32-bit pointers and 32-bit 
>ABI) on a 64-bit kernel.

The drivers/scsi/megaraid/megaraid_mm.c simply calls regular ioctl
from within the compat_ioctl, though it does copy to and from the
userland pointers. This is done by adding appropriate padding.

Sincerely,
Sreenivas
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