Re: [PATCH] drm/i915: tell the user if both KMS and UMS are disabled

From: Jani Nikula <jani.nikula@intel.com>
To: Daniel Vetter <daniel@ffwll.ch>
Cc: intel-gfx@lists.freedesktop.org
Subject: Re: [PATCH] drm/i915: tell the user if both KMS and UMS are disabled
Date: Tue, 27 May 2014 21:17:41 +0300	[thread overview]
Message-ID: <87vbsrm6gq.fsf@intel.com> (raw)
In-Reply-To: <20140527171923.GI14841@phenom.ffwll.local>

On Tue, 27 May 2014, Daniel Vetter <daniel@ffwll.ch> wrote:
> On Tue, May 27, 2014 at 07:24:12PM +0300, Jani Nikula wrote:
>> If both KMS is disabled (by i915.modeset=0 or nomodeset parameters) and
>> UMS is disabled (by CONFIG_DRM_I915_UMS=n, the default), the user might
>> not be aware his setup is not supported. Inform the users (and, by
>> extension, the poor i915 developers having to read their dmesgs in bug
>> reports) why their graphics experience might be lacking.
>> 
>> A similar message was added on the UMS path in
>> commit e147accbd19f55489dabdcc4dc3551cc3e3f2553
>> Author: Jani Nikula <jani.nikula@intel.com>
>> Date:   Thu Oct 10 15:25:37 2013 +0300
>> 
>>     drm/i915: tell the user KMS is required for gen6+
>> 
>> but it won't be reached if CONFIG_DRM_I915_UMS=n since
>> commit b30324adaf8d2e5950a602bde63030d15a61826f
>> Author: Daniel Vetter <daniel.vetter@ffwll.ch>
>> Date:   Wed Nov 13 22:11:25 2013 +0100
>> 
>>     drm/i915: Deprecated UMS support
>> 
>> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
>
> Hm, the idea is that this fails _very_ silently so that people only send
> us regression reports if they actually notice something. Since if there
> are still people out there which needs UMS, we can't yet rip it out.

My gut feeling from bug reports is that, since CONFIG_DRM_I915_UMS now
defaults to n, we mostly end up here because users have issues with KMS
and try nomodeset as a workaround. Is this silent enough, same commit
message:

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 8949fd26b0ea..ca46e6cf4b99 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -1585,6 +1585,7 @@ static int __init i915_init(void)
 		driver.get_vblank_timestamp = NULL;
 #ifndef CONFIG_DRM_I915_UMS
 		/* Silently fail loading to not upset userspace. */
+		DRM_DEBUG_DRIVER("KMS and UMS disabled.\n");
 		return 0;
 #endif
 	}

BR,
Jani.


> -Daniel
>
>> ---
>>  drivers/gpu/drm/i915/i915_drv.c | 2 ++
>>  1 file changed, 2 insertions(+)
>> 
>> diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
>> index 8949fd26b0ea..f0f690776d45 100644
>> --- a/drivers/gpu/drm/i915/i915_drv.c
>> +++ b/drivers/gpu/drm/i915/i915_drv.c
>> @@ -1584,6 +1584,8 @@ static int __init i915_init(void)
>>  	if (!(driver.driver_features & DRIVER_MODESET)) {
>>  		driver.get_vblank_timestamp = NULL;
>>  #ifndef CONFIG_DRM_I915_UMS
>> +		DRM_INFO("Kernel modesetting (KMS) and userspace modesetting (UMS) disabled\n");
>> +		DRM_INFO("See CONFIG_DRM_I915_UMS, CONFIG_DRM_I915_KMS, nomodeset, and i915.modeset parameters\n");
>>  		/* Silently fail loading to not upset userspace. */
>>  		return 0;
>>  #endif
>> -- 
>> 1.9.1
>> 
>> _______________________________________________
>> Intel-gfx mailing list
>> Intel-gfx@lists.freedesktop.org
>> http://lists.freedesktop.org/mailman/listinfo/intel-gfx
>
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> +41 (0) 79 365 57 48 - http://blog.ffwll.ch

-- 
Jani Nikula, Intel Open Source Technology Center
