[PATCH] Add -iglx & +iglx to Xserver.man

[James Jones]

On 11/25/2014 11:37 PM, Robert Morell wrote:
> On Tue, Nov 25, 2014 at 11:20:58PM -0800, Alan Coopersmith wrote:
>> On 11/25/14 10:36 PM, Robert Morell wrote:
>>> On Tue, Nov 25, 2014 at 07:26:14PM -0800, Alan Coopersmith wrote:
>>>> Covers the current state after commits 99f0365b1fbdfd9238b9f,
>>>> d0da0e9c3bb8fe0cd4879, & e3aa13b8d63ea2fba6eb4 were all applied.
>>>>
>>>> Signed-off-by: Alan Coopersmith <alan.coopersmith at oracle.com>
>>>> ---
>>>>    man/Xserver.man |   10 ++++++++++
>>>>    1 file changed, 10 insertions(+)
>>>>
>>>> diff --git a/man/Xserver.man b/man/Xserver.man
>>>> index c03830c..69ff626 100644
>>>> --- a/man/Xserver.man
>>>> +++ b/man/Xserver.man
>>>> @@ -181,6 +181,16 @@ prints a usage message.
>>>>    .B \-I
>>>>    causes all remaining command line arguments to be ignored.
>>>>    .TP 8
>>>> +.B \-iglx
>>>> +Prohibit creating indirect GLX contexts.  Indirect GLX is of limited use,
>>>> +since it only supports up to OpenGL 1.4; it's slower than direct contexts;
>>>
>>> Technically, there exists protocol for much if not all of OpenGL 2.1,
>>> and some extensions beyond that.  But not all server and client
>>> implementations support it...
>>
>> Sorry, I copied that from the comments in the commit that actually created the
>> options, and took Eric's word for it:
>>
>> http://cgit.freedesktop.org/xorg/xserver/commit/?id=99f0365b1fbdfd9238b9f5cc28491e4e6c7324f1
>>
>> Would "only fully supports up to OpenGL 1.4, with partial support for
>> OpenGL 2.1 and some later extensions" be more accurate?  Or is there
>> a better wording someone can think of?
>
> I'm not really sure myself what the extent of official
> Khronos-sanctioned protocol support is -- it's spread out over a bunch
> of extensions, and if there is any overall unifying documentation I'm
> not aware of it.
>
> Maybe a more future-proof statement appropriate for the man page would
> be something like "lacks support for many modern OpenGL features and
> extensions"?

If you want to be specific, there is enough GLX protocol approved to 
implement OpenGL 2.0.  Some of the stuff in 2.1 (PBO, mostly) is 
indefinitely awaiting a reviewer at Khronos.  If any Khronos members are 
interested in reviewing that, let me know.

However, I agree a slightly vaguer comment is probably the way to go for 
the man page.

Thanks,
-James

>>>> +and it opens a large attack surface for protocol parsing errors.
>>>> +This is the default unless +iglx is specified, though it may not be honored
>>>> +by GLX implementations other than the one provided with the X server.
>>>
>>> For what it's worth, in case anyone finds this thread in the archives,
>>> I'll point out that NVIDIA's implementation does honor this option in
>>> newer drivers, which contain the following entry in the changelog:
>>>
>>>       * Implemented support for disabling indirect GLX context creation using
>>>         the -iglx option available on X.Org server release 1.16 and newer.  Note
>>>         that future X.Org server releases may make the -iglx option the default.
>>>         To re-enable support for indirect GLX on such servers, use the +iglx
>>>         option.
>>
>> That's good - perhaps we can drop that qualification if both NVIDIA & AMD
>> will be supporting the check in their Xorg 1.17 ABI compatible versions.
>>
>> I was thinking of older driver versions when I'd written it, but obviously,
>> due to ABI changes, there shouldn't be many (any?) GLX implementations that
>> can both be loaded by Xorg 1.17 and do not support this flag, so I don't
>> know why I was thinking of that.
>
> Yeah, good point.
>
>
> - Robert
>
>>> But your text above is still accurate, so other than perhaps softening
>>> the OpenGL 1.4 limitation,
>>>
>>> Reviewed-by: Robert Morell <rmorell at nvidia.com>
>>>
>>>> +.TP 8
>>>> +.B +iglx
>>>> +Allow creating indirect GLX contexts.
>>>> +.TP 8
>>>>    .B \-maxbigreqsize \fIsize\fP
>>>>    sets the maximum big request to
>>>>    .I size
>>>> --
>>>> 1.7.9.2
>>
>>
>> --
>> 	-Alan Coopersmith-              alan.coopersmith at oracle.com
>> 	 Oracle Solaris Engineering - http://blogs.oracle.com/alanc
>>
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