11/10/2021 09:33, Chengwen Feng:

When updating the doc, we would like to change a minimum of lines,
so it's better to split lines logically: after a comma, a point,
or before the next part of the sentence.
Do not hesitate to make short lines if needed.
Such change is quite fast to do, thanks.

[...]

+* **Introduced dmadev library with:**
+
+  * Device allocation functions.

You can drop this line, it is not a feature.

[...]

+static int
+dma_dev_data_prepare(void)
+{
+	size_t size;
+
+	if (rte_dma_devices != NULL)
+		return 0;
+
+	size = dma_devices_max * sizeof(struct rte_dma_dev);
+	rte_dma_devices = malloc(size);
+	if (rte_dma_devices == NULL)
+		return -ENOMEM;
+	memset(rte_dma_devices, 0, size);
+
+	return 0;
+}
+
+static int
+dma_data_prepare(void)
+{
+	if (dma_devices_max == 0)
+		dma_devices_max = RTE_DMADEV_DEFAULT_MAX;
+	return dma_dev_data_prepare();
+}
+
+static struct rte_dma_dev *
+dma_allocate(const char *name, int numa_node, size_t private_data_size)
+{
+	struct rte_dma_dev *dev;
+	void *dev_private;
+	int16_t dev_id;
+	int ret;
+
+	ret = dma_data_prepare();
+	if (ret < 0) {
+		RTE_DMA_LOG(ERR, "Cannot initialize dmadevs data");
+		return NULL;
+	}
+
+	dev = dma_find_by_name(name);
+	if (dev != NULL) {
+		RTE_DMA_LOG(ERR, "DMA device already allocated");
+		return NULL;
+	}
+
+	dev_private = rte_zmalloc_socket(name, private_data_size,
+					 RTE_CACHE_LINE_SIZE, numa_node);
+	if (dev_private == NULL) {
+		RTE_DMA_LOG(ERR, "Cannot allocate private data");
+		return NULL;
+	}
+
+	dev_id = dma_find_free_id();
+	if (dev_id < 0) {
+		RTE_DMA_LOG(ERR, "Reached maximum number of DMA devices");
+		rte_free(dev_private);
+		return NULL;
+	}
+
+	dev = &rte_dma_devices[dev_id];
+	rte_strscpy(dev->dev_name, name, sizeof(dev->dev_name));
+	dev->dev_id = dev_id;
+	dev->numa_node = numa_node;
+	dev->dev_private = dev_private;
+
+	return dev;
+}
+
+static void
+dma_release(struct rte_dma_dev *dev)
+{
+	rte_free(dev->dev_private);
+	memset(dev, 0, sizeof(struct rte_dma_dev));
+}
+
+struct rte_dma_dev *
+rte_dma_pmd_allocate(const char *name, int numa_node, size_t private_data_size)
+{
+	struct rte_dma_dev *dev;
+
+	if (dma_check_name(name) != 0 || private_data_size == 0)
+		return NULL;
+
+	dev = dma_allocate(name, numa_node, private_data_size);
+	if (dev == NULL)
+		return NULL;
+
+	dev->state = RTE_DMA_DEV_REGISTERED;
+
+	return dev;
+}
+
+int
+rte_dma_pmd_release(const char *name)
+{
+	struct rte_dma_dev *dev;
+
+	if (dma_check_name(name) != 0)
+		return -EINVAL;
+
+	dev = dma_find_by_name(name);
+	if (dev == NULL)
+		return -EINVAL;
+
+	dma_release(dev);
+	return 0;
+}

Trying to understand the logic of creation/destroy.
skeldma_probe
\-> skeldma_create
    \-> rte_dma_pmd_allocate
        \-> dma_allocate
            \-> dma_data_prepare
                \-> dma_dev_data_prepare
skeldma_remove
\-> skeldma_destroy
    \-> rte_dma_pmd_release
        \-> dma_release
app
\-> rte_dma_close
    \-> skeldma_close
    \-> dma_release

My only concern is that the PMD remove does not call rte_dma_close.
The PMD should check which dmadev is open for the rte_device to remove,
and close the dmadev first.
This way, no need for the function rte_dma_pmd_release,
and no need to duplicate the release process in two paths.
By the way, the function vchan_release is called only in the close function,
not in the "remove path".