[PATCH 4/5] Update linux/ioctlent.h.in file

[Gabriel Laskar]

On Fri, Jan 16, 2015 at 3:41 PM, Dmitry V. Levin <ldv at altlinux.org> wrote:
> On Fri, Jan 16, 2015 at 09:49:19AM +0100, Gabriel Laskar wrote:
>> On Fri, Jan 16, 2015 at 12:39 AM, Dmitry V. Levin wrote:
> [...]
>> > strace uses only 16 bits (8-bit number and 8-bit type) of the 32-bit ioctl
>> > command, so the only real solution to this issue is to take into account
>> > remaining 16 bits (size and direction).
>> >
>> > For example,
>> > SNDCTL_TMR_TIMEBASE is _IOC(_IOC_READ|_IOC_WRITE, 'T', 1, sizeof(int)),
>> > SNDRV_TIMER_IOCTL_NEXT_DEVICE is _IOC(_IOC_READ|_IOC_WRITE, 'T', 1, sizeof(struct snd_timer_id)),
>> > TCGETS is architecture-specific, its generic value 0x5401 is _IOC(0, 'T', 1, 0).
>> >
>> > As you can see all these 32-bit values are different.
>> > The only question is how to evaluate these remaining bits reliably, especially
>> > 14 bits (or 13 on alpha, mips, powerpc, and sparc) of ioctl command size.
>>
>> Or we could do that, yes. I don't know why I have occulted this
>> solution. I have missed the 14/13 bit snafu though.
>>
>> Maybe we can create 2 ioctlent.h.in files, 1 for the 14 bits size, and
>> another one for the 13 bits one and compile the right one for each
>> arch.
>
> If we succeeded to fetch the "size" bits, we could avoid these
> architecture-specific complications by storing {dir,type,nr,size}
> in ioctlent.h.in files apart, and assembling them into 32-bit words
> at build time.
> This way we won't need two different generic ioctlent.h.in files.
>
> We still have to support small architecture-specific ioctlent.h.in
> files because some historic ioctl commands like TCGETS differ.

Seems good. I will give it a go.

Beside that issue that was already present without these patches, is
there any comments on this serie ?

-- 
Gabriel Laskar