Re: [PATCH v3 2/3] dma/ae4dma: add control path operations

[fengchengwen <fengchengwen@huawei.com>]

On 6/29/2026 12:04 AM, Stephen Hemminger wrote:
> On Sat, 27 Jun 2026 08:09:09 +0800
> fengchengwen <fengchengwen@huawei.com> wrote:
> 
>>>  
>>> +static int
>>> +ae4dma_dev_configure(struct rte_dma_dev *dev __rte_unused,
>>> +		const struct rte_dma_conf *dev_conf,
>>> +		uint32_t conf_sz)
>>> +{
>>> +	if (sizeof(struct rte_dma_conf) != conf_sz)
>>> +		return -EINVAL;  
>>
>> This may break ABI compatible
> 
> Ignore that suggestion. This is a reasonable way to handle new configuration
> functions. You need/want a minimal set of values. If rte_dma_conf grows in size
> then the code can add compatability; by requiring a minimum set of values
> and then setting the rest to zero.
> 
> Something like
> 
> static int
> ae4dma_dev_configure(struct rte_dma_dev *dev __rte_unused,
> 		const struct rte_dma_conf *dev_conf,
> 		size_t conf_sz)
> {
> 	if (conf_sz < sizeof(struct orig_rte_dma_conf))
> 		return -EINVAL;

+1 for this

> 
> 	struct rte_dma_conf conf;
> 	memcpy(&conf, dev_conf, RTE_MIN(conf_sz, sizeof(conf)));
>         dev_conf = &conf;
> 
> Looking at rte_dma_conf the structure has holes and dmadev lib
> doesn't validate undefined flags, so it already has future ABI problems.

Yes, it indeed