[Mesa-dev] [PATCH] gbm: Replace GBM_DRIVERS_PATH with LIBGL_DRIVERS_PATH

[Kristian Høgsberg]

On Sun, Jul 20, 2014 at 11:36 PM, Eric Anholt <eric at anholt.net> wrote:
> Emil Velikov <emil.l.velikov at gmail.com> writes:
>
>> On 18/07/14 17:27, Kenneth Graunke wrote:
>>> On Friday, July 18, 2014 07:41:57 AM Dylan Baker wrote:
>>>> Currently mesa searches for two different environment variables,
>>>> LIBGL_DRIVERS_PATH and GBM_DRIVERS_PATH. The first is used for search
>>>> for DRI drivers in every case except GBM, and the latter is used
>>>> exclusively for setting GBM drivers. This patch simplifies things by
>>>> having just one variable to set.
>>>>
>>>> Signed-off-by: Dylan Baker <baker.dylan.c at gmail.com>
>>>> ---
>>>>  src/gbm/backends/dri/gbm_dri.c | 4 ++--
>>>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/src/gbm/backends/dri/gbm_dri.c b/src/gbm/backends/dri/gbm_dri.c
>>>> index 347bc99..9d9d1c4 100644
>>>> --- a/src/gbm/backends/dri/gbm_dri.c
>>>> +++ b/src/gbm/backends/dri/gbm_dri.c
>>>> @@ -212,8 +212,8 @@ dri_load_driver(struct gbm_dri_device *dri)
>>>>
>>>>     search_paths = NULL;
>>>>     if (geteuid() == getuid()) {
>>>> -      /* don't allow setuid apps to use GBM_DRIVERS_PATH */
>>>> -      search_paths = getenv("GBM_DRIVERS_PATH");
>>>> +      /* don't allow setuid apps to use LIBGL_DRIVERS_PATH */
>>>> +      search_paths = getenv("LIBGL_DRIVERS_PATH");
>>>>     }
>>>>     if (search_paths == NULL)
>>>>        search_paths = DEFAULT_DRIVER_DIR;
>>>>
>>>
>>> I'm definitely a fan of moving to LIBGL_DRIVERS_PATH for everything - GBM_DRIVERS_PATH is just another environment variable to forget to set properly.
>>>
>>> As is, this is:
>>> Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>
>>>
>>> Are people okay with just moving to LIBGL_DRIVERS_PATH completely like this?  Or do people want it to check GBM_DRIVERS_PATH then fall back to LIBGL_DRIVERS_PATH?  Or use $GBM_DRIVERS_PATH:$LIBGL_DRIVERS_PATH?
>>>
>> A few thoughts of a blurry mind (sorry I'm out of coffee):
>>
>> I can envision at least at couple of use-cases where either of the above will
>> cause more harm than good, yet I feel that affected people will come here
>> after spending hours of debugging/bisecting.
>>
>> IMHO the "one variable to rule them all" while convenient (set only
>> LIBGL_DRIVERS_PATH in your debug scripts/session), is not at all useful. If
>> the only issue is "I always forget to set it", I believe that it's not a thing
>> that should be addressed in mesa.
>
> I definitely lost out recently because there are two different
> variables, and I can't come up with any reason to have two.  What cases
> are you thinking of?

It's a historical accident more than anything.  It wasn't designed to
work this way for any particular reason.  My only comment is that we
should try getenv("GBM..") if getenv("LIBGL..) returns NULL.  That
doesn't seem like a big maintenance burden and avoids breaking
anybodys scripts.

Kristian