[FFmpeg-devel] [PATCH 2/2] hwcontext_vulkan: expose the enabled device features

[Lynne]

May 19, 2020, 20:57 by sw at jkqxz.net:

> On 13/05/2020 16:53, Lynne wrote:
>
>> With this, the puzze of making libplacebo, ffmpeg and any other Vulkan 
>> API users interoperable is complete.
>> Users of both libraries can initialize one another's contexts without having
>> to create a new one.
>> > From 28264793295b0d7861527f40fa7c7041a3b34907 Mon Sep 17 00:00:00 2001
>> From: Lynne <dev at lynne.ee>
>> Date: Wed, 13 May 2020 16:39:00 +0100
>> Subject: [PATCH 2/2] hwcontext_vulkan: expose the enabled device features
>>
>> With this, the puzze of making libplacebo, ffmpeg and any other Vulkan
>>
>
> The "puzze".
>

Fixed.



>> API users interoperable is complete.
>> Users of both libraries can initialize one another's contexts without having
>> to create a new one.
>> ---
>>  libavutil/hwcontext_vulkan.c | 11 +++++++++++
>>  libavutil/hwcontext_vulkan.h |  7 +++++++
>>  2 files changed, 18 insertions(+)
>>
>> diff --git a/libavutil/hwcontext_vulkan.c b/libavutil/hwcontext_vulkan.c
>> index 82ceb7013a..d05dd2cf5d 100644
>> --- a/libavutil/hwcontext_vulkan.c
>> +++ b/libavutil/hwcontext_vulkan.c
>> @@ -807,6 +807,7 @@ static int vulkan_device_create_internal(AVHWDeviceContext *ctx,
>>  AVDictionaryEntry *opt_d;
>>  VulkanDevicePriv *p = ctx->internal->priv;
>>  AVVulkanDeviceContext *hwctx = ctx->hwctx;
>> +    VkPhysicalDeviceFeatures dev_features = { 0 };
>>  VkDeviceQueueCreateInfo queue_create_info[3] = {
>>  { .sType = VK_STRUCTURE_TYPE_DEVICE_QUEUE_CREATE_INFO, },
>>  { .sType = VK_STRUCTURE_TYPE_DEVICE_QUEUE_CREATE_INFO, },
>> @@ -815,6 +816,7 @@ static int vulkan_device_create_internal(AVHWDeviceContext *ctx,
>>  
>>  VkDeviceCreateInfo dev_info = {
>>  .sType                = VK_STRUCTURE_TYPE_DEVICE_CREATE_INFO,
>> +        .pEnabledFeatures     = &hwctx->device_features,
>>  .pQueueCreateInfos    = queue_create_info,
>>  .queueCreateInfoCount = 0,
>>  };
>> @@ -839,6 +841,15 @@ static int vulkan_device_create_internal(AVHWDeviceContext *ctx,
>>  av_log(ctx, AV_LOG_VERBOSE, "    minMemoryMapAlignment:              %li\n",
>>  p->props.limits.minMemoryMapAlignment);
>>  
>> +    vkGetPhysicalDeviceFeatures(hwctx->phys_dev, &dev_features);
>> +#define COPY_FEATURE(DST, NAME) (DST).NAME = dev_features.NAME;
>> +    COPY_FEATURE(hwctx->device_features, shaderImageGatherExtended)
>> +    COPY_FEATURE(hwctx->device_features, shaderStorageImageExtendedFormats)
>> +    COPY_FEATURE(hwctx->device_features, fragmentStoresAndAtomics)
>> +    COPY_FEATURE(hwctx->device_features, vertexPipelineStoresAndAtomics)
>> +    COPY_FEATURE(hwctx->device_features, shaderInt64)
>> +#undef COPY_FEATURE
>>
>
> Forgive me if I'm being stupid here, but why can't the user run exactly the same code to find the features themselves?  They do have hwctx->phys_dev.
>

vkGetPhysicalDeviceFeatures gets the list of features the device supports.
You have to manually put the ones you enable in the VkDeviceCreateInfo struct.
Even after you do that, vkGetPhysicalDeviceFeatures still gives you the features the device
supports, not what you've enabled. There's no way to get any enabled features or extensions
for a device or an instance after its created, but only what's supported.



>> +
>>  /* Search queue family */
>>  if ((err = search_queue_families(ctx, &dev_info)))
>>  goto end;
>> diff --git a/libavutil/hwcontext_vulkan.h b/libavutil/hwcontext_vulkan.h
>> index 9fbe8b9dcb..b73097d514 100644
>> --- a/libavutil/hwcontext_vulkan.h
>> +++ b/libavutil/hwcontext_vulkan.h
>> @@ -94,6 +94,13 @@ typedef struct AVVulkanDeviceContext {
>>  */
>>  const char * const *enabled_dev_extensions;
>>  int nb_enabled_dev_extensions;
>> +    /**
>> +     * This structure lists all device features that are present and enabled
>> +     * during device creation. By default, if present, shaderImageGatherExtended,
>> +     * shaderStorageImageExtendedFormats, fragmentStoresAndAtomics, shaderInt64,
>> +     * and vertexPipelineStoresAndAtomics are enabled.
>>
>
> And what should an API user set it to?  Do they need to enable that same set of features?
>

The API user can set it to whatever they have enabled in their VkDeviceCreateInfo struct.
They don't need to have the same extensions enabled. We don't (and won't) depend on any
extensions, but optionally use them if they're enabled.
Not sure how to make this clearer.