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Subject: Re: [PATCH] Revert "drm/qxl: drop prime import/export callbacks"
To:     Daniel Vetter <daniel@ffwll.ch>, Gerd Hoffmann <kraxel@redhat.com>
Cc:     David Airlie <airlied@linux.ie>,
        open list <linux-kernel@vger.kernel.org>,
        dri-devel <dri-devel@lists.freedesktop.org>,
        "open list:DRM DRIVER FOR QXL VIRTUAL GPU" 
        <virtualization@lists.linux-foundation.org>,
        "open list:DRM DRIVER FOR QXL VIRTUAL GPU" 
        <spice-devel@lists.freedesktop.org>,
        David Airlie <airlied@redhat.com>
References: <20190426053324.26443-1-kraxel@redhat.com>
 <CAKMK7uG+vMU0hqqiKAswu=LqpkcXtLPqbYLRWgoAPpsQQV4qzA@mail.gmail.com>
From:   Thomas Hellstrom <thomas@shipmail.org>
Message-ID: <8ae152fe-7811-4de3-e26f-350650a8f992@shipmail.org>
Date:   Fri, 26 Apr 2019 17:42:23 +0200
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On 4/26/19 4:21 PM, Daniel Vetter wrote:
> On Fri, Apr 26, 2019 at 7:33 AM Gerd Hoffmann <kraxel@redhat.com> wrote:
>> This reverts commit f4c34b1e2a37d5676180901fa6ff188bcb6371f8.
>>
>> Simliar to commit a0cecc23cfcb Revert "drm/virtio: drop prime
>> import/export callbacks".  We have to do the same with qxl,
>> for the same reasons (it breaks DRI3).
>>
>> Drop the WARN_ON_ONCE().
>>
>> Fixes: f4c34b1e2a37d5676180901fa6ff188bcb6371f8
>> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
> Maybe we need some helpers for virtual drivers which only allow
> self-reimport and nothing else at all? I think there's qxl, virgl,
> vmwgfx and maybe also vbox one who could use this ... Just a quick
> idea.
> -Daniel

I think vmwgfx could, in theory, support the full range of operations,
at least for reasonably recent device versions. However, it wouldn't be 
terribly efficient since the exported dma-buf sglist would basically be 
a bounce-buffer.

/Thomas


>> ---
>>   drivers/gpu/drm/qxl/qxl_drv.c   |  4 ++++
>>   drivers/gpu/drm/qxl/qxl_prime.c | 12 ++++++++++++
>>   2 files changed, 16 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/qxl/qxl_drv.c b/drivers/gpu/drm/qxl/qxl_drv.c
>> index 578d867a81d5..f33e349c4ec5 100644
>> --- a/drivers/gpu/drm/qxl/qxl_drv.c
>> +++ b/drivers/gpu/drm/qxl/qxl_drv.c
>> @@ -255,10 +255,14 @@ static struct drm_driver qxl_driver = {
>>   #if defined(CONFIG_DEBUG_FS)
>>          .debugfs_init = qxl_debugfs_init,
>>   #endif
>> +       .prime_handle_to_fd = drm_gem_prime_handle_to_fd,
>> +       .prime_fd_to_handle = drm_gem_prime_fd_to_handle,
>>          .gem_prime_export = drm_gem_prime_export,
>>          .gem_prime_import = drm_gem_prime_import,
>>          .gem_prime_pin = qxl_gem_prime_pin,
>>          .gem_prime_unpin = qxl_gem_prime_unpin,
>> +       .gem_prime_get_sg_table = qxl_gem_prime_get_sg_table,
>> +       .gem_prime_import_sg_table = qxl_gem_prime_import_sg_table,
>>          .gem_prime_vmap = qxl_gem_prime_vmap,
>>          .gem_prime_vunmap = qxl_gem_prime_vunmap,
>>          .gem_prime_mmap = qxl_gem_prime_mmap,
>> diff --git a/drivers/gpu/drm/qxl/qxl_prime.c b/drivers/gpu/drm/qxl/qxl_prime.c
>> index 8b448eca1cd9..114653b471c6 100644
>> --- a/drivers/gpu/drm/qxl/qxl_prime.c
>> +++ b/drivers/gpu/drm/qxl/qxl_prime.c
>> @@ -42,6 +42,18 @@ void qxl_gem_prime_unpin(struct drm_gem_object *obj)
>>          qxl_bo_unpin(bo);
>>   }
>>
>> +struct sg_table *qxl_gem_prime_get_sg_table(struct drm_gem_object *obj)
>> +{
>> +       return ERR_PTR(-ENOSYS);
>> +}
>> +
>> +struct drm_gem_object *qxl_gem_prime_import_sg_table(
>> +       struct drm_device *dev, struct dma_buf_attachment *attach,
>> +       struct sg_table *table)
>> +{
>> +       return ERR_PTR(-ENOSYS);
>> +}
>> +
>>   void *qxl_gem_prime_vmap(struct drm_gem_object *obj)
>>   {
>>          struct qxl_bo *bo = gem_to_qxl_bo(obj);
>> --
>> 2.18.1
>>
>