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Date: Fri, 16 Jul 2021 15:41:39 +0100
From: Bruce Richardson <bruce.richardson@intel.com>
To: Chengwen Feng <fengchengwen@huawei.com>
Cc: thomas@monjalon.net, ferruh.yigit@intel.com, jerinj@marvell.com,
 jerinjacobk@gmail.com, andrew.rybchenko@oktetlabs.ru, dev@dpdk.org,
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 hemant.agrawal@nxp.com, maxime.coquelin@redhat.com,
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References: <1625231891-2963-1-git-send-email-fengchengwen@huawei.com>
 <1626403535-40051-1-git-send-email-fengchengwen@huawei.com>
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Subject: Re: [dpdk-dev] [PATCH v5] dmadev: introduce DMA device library
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On Fri, Jul 16, 2021 at 10:45:35AM +0800, Chengwen Feng wrote:
> This patch introduce 'dmadevice' which is a generic type of DMA
> device.
> 
> The APIs of dmadev library exposes some generic operations which can
> enable configuration and I/O with the DMA devices.
> 
> Signed-off-by: Chengwen Feng <fengchengwen@huawei.com>
> ---
<snip>
> +
> +static struct rte_dmadev *
> +dmadev_allocate(const char *name)
> +{
> +	struct rte_dmadev *dev;
> +	uint16_t dev_id;
> +
> +	dev = dmadev_find(name);
> +	if (dev != NULL) {
> +		RTE_DMADEV_LOG(ERR, "DMA device already allocated\n");
> +		return NULL;
> +	}
> +
> +	dev_id = dmadev_find_free_dev();
> +	if (dev_id == RTE_DMADEV_MAX_DEVS) {
> +		RTE_DMADEV_LOG(ERR, "Reached maximum number of DMA devices\n");
> +		return NULL;
> +	}
> +
> +	if (dmadev_shared_data_prepare() != 0) {
> +		RTE_DMADEV_LOG(ERR, "Cannot allocate DMA shared data\n");
> +		return NULL;
> +	}
> +
The order of the "shared_data_prepare" and "find_free_dev" calls needs to
be reversed. When calling allocate for the first dmadev driver you will get
a segfault in find function, since it accesses the shared data which has
not been created yet.

Regards,
/Bruce