[PATCH v3 26/32] drm/via: Add via_drm.h

Thomas Zimmermann tzimmermann at suse.de
Tue Aug 2 11:38:26 UTC 2022 

Hi

Am 02.08.22 um 05:45 schrieb Kevin Brace:
> Hi Thomas,
> 
> I hope I am comprehending this right.
> Yes, I am adding 3 new uAPI calls, not 6 of them.
> Correspondingly, there are 3 new structs added.

That's understood.

> While I may drop one (unmap uAPI), I personally do not wish to drop the other two at this point.
> Instead, I may need to add setparam and / or getparam uAPI to pass PCI Device ID back to the userspace.
> This is mainly needed by Mesa, although there is no code for Mesa at this point.

Exactly my point! There's no userspace for it. That's why Sam and me are 
asking you to remove all kinds if uapi changes or ioctls from the 
patchset until Mesa (or some other component) requires it.

> I fear dropping the remaining two will require substantial redesign, and I will like to avoid this since the code is already working.

No, it won't require a redesign. You'll have to remove the changes to 
the uapi header and any new ioctls that are in the patchset. Userspace 
programs; such as X11's modesetting driver, Weston or Gnome; will use 
the kernel's dumb-buffer ioctls to create unaccelerated buffers.  You 
won't need any via-specific code in userspace. It's all there already 
and fully driver independent. Mesa will do software rendering.  For the 
kernel's dumb buffers, please see [1].

> It is my plan to proceed to adding acceleration after the code is added to the mainline kernel tree, so I will like to do it the way it is set up now.

You can still send the current uapi changes when you add 3d acceleration 
to the kernel and Mesa.  But once these interfaces have been added to 
the kernel, they are nearly impossible to change or remove. That's why 
we don't want to do this now.

Best regards
Thomas

[1] 
https://www.kernel.org/doc/html/latest/gpu/drm-kms.html#dumb-buffer-objects

> 
> Regards,
> 
> Kevin Brace
> Brace Computer Laboratory blog
> https://bracecomputerlab.com
> 
> 
>> Sent: Monday, August 01, 2022 at 11:49 AM
>> From: "Thomas Zimmermann" <tzimmermann at suse.de>
>> To: "Kevin Brace" <kevinbrace at gmx.com>
>> Cc: dri-devel at lists.freedesktop.org
>> Subject: Re: [PATCH v3 26/32] drm/via: Add via_drm.h
>>
>> Hi Kevin
>>
>> Am 31.07.22 um 00:48 schrieb Kevin Brace:
>>> Hi Thomas,
>>>
>>> I cannot drop the older DRI1 based uAPI calls.
>>> This is because include/uapi/drm/via_drm.h needs to retain backward compatibility with the existing OpenChrome DDX's XvMC library (it gets compiled when OpenChrome DDX is built) and likely with the existing DDX Xv code as well.
>>> If I remove the DRI1 based uAPI calls, the XvMC library will not get compiled (compile error will occur since the XvMC library assumes the presence of DRI1 based uAPI), and I assume the same for the DDX Xv code (I cannot even reach here since the XvMC library is compiled first).
>>> Although the v3 patch does not contain it, v4 patch will utilize drm_invalid_op() for the discontinued (not deprecated since OpenChrome DRM does not support the older DRI1 based uAPI at all) DRI1 based uAPI.
>>>
>>> https://cgit.freedesktop.org/openchrome/drm-openchrome/commit/?h=drm-next-5.20&id=16b3d68f95c9ccd15b7a3310e5d752fabbc76518
>>>
>>> drm_invalid_op() is related to drm_ioctl.c, and is meant for legacy DRMs like Radeon, i915, etc.
>>> Since OpenChrome DRM is not a clean sheet design (related to VIA DRM to some extent), I will use this function for properly handling discontinued legacy uAPI calls.
>>> I hope this explanation / reasoning is okay with you.
>>
>> I'm not sure I understand your reply ormaybe I'm just missing something
>> here.
>>
>> I'm not asking you to remove the existing DRI1 uapi. I'm just asking to
>> not add the 6 new _GEM_ defines and 3 new _gem_ structures now.  You
>> mentioned that the driver does not yet support acceleration of any kind.
>> So there should be no need to extend to uapi now.  You can still do this
>> when you add acceleration to the driver.
>>
>> Until then, the Xorg modesetting driver or any Compositor can use the
>> generic dumb-buffer ioctls that create buffers with no acceleration.
>>
>> Best regards
>> Thomas
>>
>>>
>>> Regards,
>>>
>>> Kevin Brace
>>> Brace Computer Laboratory blog
>>> https://bracecomputerlab.com
>>>
>>>> Sent: Tuesday, July 26, 2022 at 11:24 AM
>>>> From: "Thomas Zimmermann" <tzimmermann at suse.de>
>>>> To: "Kevin Brace" <kevinbrace at gmx.com>, dri-devel at lists.freedesktop.org
>>>> Cc: "Kevin Brace" <kevinbrace at bracecomputerlab.com>
>>>> Subject: Re: [PATCH v3 26/32] drm/via: Add via_drm.h
>>>>
>>>> Hi
>>>>
>>>> Am 26.07.22 um 01:53 schrieb Kevin Brace:
>>>>> From: Kevin Brace <kevinbrace at bracecomputerlab.com>
>>>>>
>>>>> Changed the uAPI.
>>>>>
>>>>> Signed-off-by: Kevin Brace <kevinbrace at bracecomputerlab.com>
>>>>> ---
>>>>>     include/uapi/drm/via_drm.h | 35 +++++++++++++++++++++++++++++++----
>>>>>     1 file changed, 31 insertions(+), 4 deletions(-)
>>>>>
>>>>> diff --git a/include/uapi/drm/via_drm.h b/include/uapi/drm/via_drm.h
>>>>> index a1e125d42208..e9da45ce130a 100644
>>>>> --- a/include/uapi/drm/via_drm.h
>>>>> +++ b/include/uapi/drm/via_drm.h
>>>>> @@ -1,4 +1,5 @@
>>>>>     /*
>>>>> + * Copyright © 2020 Kevin Brace
>>>>>      * Copyright 1998-2003 VIA Technologies, Inc. All Rights Reserved.
>>>>>      * Copyright 2001-2003 S3 Graphics, Inc. All Rights Reserved.
>>>>>      *
>>>>> @@ -16,10 +17,10 @@
>>>>>      * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
>>>>>      * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
>>>>>      * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
>>>>> - * VIA, S3 GRAPHICS, AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
>>>>> - * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
>>>>> - * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
>>>>> - * DEALINGS IN THE SOFTWARE.
>>>>> + * THE AUTHORS, COPYRIGHT HOLDERS, AND/OR ITS SUPPLIERS BE LIABLE FOR ANY
>>>>> + * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT
>>>>> + * OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR
>>>>> + * THE USE OR OTHER DEALINGS IN THE SOFTWARE.
>>>>>      */
>>>>>     #ifndef _VIA_DRM_H_
>>>>>     #define _VIA_DRM_H_
>>>>> @@ -81,6 +82,11 @@ extern "C" {
>>>>>     #define DRM_VIA_DMA_BLIT        0x0e
>>>>>     #define DRM_VIA_BLIT_SYNC       0x0f
>>>>>
>>>>> +#define	DRM_VIA_GEM_CREATE	0x10
>>>>> +#define	DRM_VIA_GEM_MAP		0x11
>>>>> +#define	DRM_VIA_GEM_UNMAP	0x12
>>>>
>>>> This looks a lot like ioctl ops for using accelerated HW buffers. But
>>>> the patch is near the end of the series and you said in the series'
>>>> cover letter that there's no acceleration. I suspect that these
>>>> constants are currently unused?  If so, please drop the patch from the
>>>> series. If can be merged later when something really depends on it.
>>>>
>>>> Best regards
>>>> Thomas
>>>>
>>>>> +
>>>>> +
>>>>>     #define DRM_IOCTL_VIA_ALLOCMEM	  DRM_IOWR(DRM_COMMAND_BASE + DRM_VIA_ALLOCMEM, drm_via_mem_t)
>>>>>     #define DRM_IOCTL_VIA_FREEMEM	  DRM_IOW( DRM_COMMAND_BASE + DRM_VIA_FREEMEM, drm_via_mem_t)
>>>>>     #define DRM_IOCTL_VIA_AGP_INIT	  DRM_IOWR(DRM_COMMAND_BASE + DRM_VIA_AGP_INIT, drm_via_agp_t)
>>>>> @@ -97,6 +103,10 @@ extern "C" {
>>>>>     #define DRM_IOCTL_VIA_DMA_BLIT    DRM_IOW(DRM_COMMAND_BASE + DRM_VIA_DMA_BLIT, drm_via_dmablit_t)
>>>>>     #define DRM_IOCTL_VIA_BLIT_SYNC   DRM_IOW(DRM_COMMAND_BASE + DRM_VIA_BLIT_SYNC, drm_via_blitsync_t)
>>>>>
>>>>> +#define	DRM_IOCTL_VIA_GEM_CREATE	DRM_IOWR(DRM_COMMAND_BASE + DRM_VIA_GEM_CREATE, struct drm_via_gem_create)
>>>>> +#define	DRM_IOCTL_VIA_GEM_MAP		DRM_IOWR(DRM_COMMAND_BASE + DRM_VIA_GEM_MAP, struct drm_via_gem_map)
>>>>> +#define	DRM_IOCTL_VIA_GEM_UNMAP		DRM_IOR(DRM_COMMAND_BASE + DRM_VIA_GEM_UNMAP, struct drm_via_gem_unmap)
>>>>> +
>>>>>     /* Indices into buf.Setup where various bits of state are mirrored per
>>>>>      * context and per buffer.  These can be fired at the card as a unit,
>>>>>      * or in a piecewise fashion as required.
>>>>> @@ -275,6 +285,23 @@ typedef struct drm_via_dmablit {
>>>>>     	drm_via_blitsync_t sync;
>>>>>     } drm_via_dmablit_t;
>>>>>
>>>>> +struct drm_via_gem_create {
>>>>> +	uint64_t size;
>>>>> +	uint32_t alignment;
>>>>> +	uint32_t domain;
>>>>> +	uint32_t handle;
>>>>> +	uint64_t offset;
>>>>> +};
>>>>> +
>>>>> +struct drm_via_gem_map {
>>>>> +	uint32_t handle;
>>>>> +	uint64_t map_offset;
>>>>> +};
>>>>> +
>>>>> +struct drm_via_gem_unmap {
>>>>> +	uint32_t handle;
>>>>> +};
>>>>> +
>>>>>     #if defined(__cplusplus)
>>>>>     }
>>>>>     #endif
>>>>> --
>>>>> 2.35.1
>>>>>
>>>>
>>>> -- 
>>>> Thomas Zimmermann
>>>> Graphics Driver Developer
>>>> SUSE Software Solutions Germany GmbH
>>>> Maxfeldstr. 5, 90409 Nürnberg, Germany
>>>> (HRB 36809, AG Nürnberg)
>>>> Geschäftsführer: Ivo Totev
>>>>
>>
>> -- 
>> Thomas Zimmermann
>> Graphics Driver Developer
>> SUSE Software Solutions Germany GmbH
>> Maxfeldstr. 5, 90409 Nürnberg, Germany
>> (HRB 36809, AG Nürnberg)
>> Geschäftsführer: Ivo Totev
>>

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev
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