Re: [PATCH 1/3] IR: add core lirc device interface

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On Jun 4, 2010, at 10:45 PM, Jarod Wilson <jarod@xxxxxxxxxxxx> wrote:

On Fri, Jun 4, 2010 at 7:16 PM, Jon Smirl <jonsmirl@xxxxxxxxx> wrote:
On Fri, Jun 4, 2010 at 5:17 PM, Jarod Wilson <jarod@xxxxxxxxxxxx> wrote:
On Fri, Jun 4, 2010 at 4:17 PM, Jarod Wilson <jarod@xxxxxxxxxx> wrote:
On Fri, Jun 04, 2010 at 02:57:04PM -0400, Jon Smirl wrote:
...
From what I'm seeing, those are the current used ioctls:

+#define LIRC_GET_FEATURES _IOR('i', 0x00000000, unsigned long) +#define LIRC_GET_LENGTH _IOR('i', 0x0000000f, unsigned long)

Has this been set into stone yet? if not a 64b word would be more future proof.

Nope, not set in stone at all, nothing has been merged. A patch I was carrying in Fedora changed all unsigned long to u64 and unsigned int to u32, and my current ir wip tree has all u32, but I don't see a reason why if we're going to make a change, it couldn't be to all u64, for as much
future-proofing as possible.

Hrm, struct file_operations specifies an unsigned long for the ioctl
args, so doesn't that mean we're pretty much stuck with only 32-bit
for the ioctls?

I haven't written an IOCTL in a while, but how would you pass a 64b
memory address?

Well, you wouldn't use struct file_operations' ioctl definition if you
wanted to do so on a 32-bit host. :)

Its definitely possible using a different ioctl definition (see
gdth_ioctl_free in drivers/scsi/gdth_proc.c, for example), but we're
currently bound by what's there for file_operations.

There's also the two-pass approach. Just split the address (or feature flags) across two slightly different ioctl cmds.

--
Jarod Wilson
jarod@xxxxxxxxxxxx

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