金屬紋理格式bgra8Unorm\U srgb在金屬系列2 GPU上不可寫

我將一個帶有MTLPixelFormat.bgra8Unorm_srgb的紋理傳遞給一個計算著色器，該著色器對此紋理有一個texture2d<float, access::write>。我得到以下錯誤：

• validateComputeFunctionArguments:818: failed assertion Compute Function(rescaleTexture): Non-writeable texture format MTLPixelFormat.BGRA8Unorm_sRGB is being bound at index 1 to a shader argument with write access enabled.

我有一個“Metal Family 2 GPU”（Intel Iris Plus Graphics 640，Metal Family:Supported，Metal GPUFamily macOS 2），根據(jù)蘋果的文檔，具有MTLPixelFormat.BGRA8Unorm_sRGB像素格式的紋理應(yīng)該是可寫的。

我做錯了什么？

以下是我用來創(chuàng)建紋理的（部分）代碼：

let desc = MTLTextureDescriptor.texture2DDescriptor(
    pixelFormat: MTLPixelFormat.bgra8Unorm_srgb,
    width: outputTextureWidth,
    height: outputTextureHeight,
    mipmapped: false)
desc.usage = [.shaderRead, .shaderWrite]
let tex = device.makeTexture(descriptor: desc)

以下是著色器代碼的（一部分）：

kernel void
rescaleTexture(texture2d<float, access::sample> source [[texture(0)]],
               texture2d<float, access::write> target [[texture(1)]],
               uint2 id [[thread_position_in_grid]])
{
    if (id.x >= target.get_width() || id.y >= target.get_height()) {
        return;
    }

    const float u = (float)id.x / (target.get_width () - 1);
    const float v = (float)id.y / (target.get_height () - 1);

    target.write (source.sample (sampler_linear_no_mipmap, float2 (u, v)), id);
}